Abstract
Introduction: Theoretical Framework
Motivation to learn in school is a well-known problem, particularly in science, where students exhibit a decline in interest in the subject, lack of deep understanding, an inability to use school knowledge, and overall apathy for school-related learning (James & Williams, 2017; Programme for International Student Assessment [PISA] reports by the Organisation for Economic Co-Operation and Development [OECD]; Rocard et al., 2007). Hungarian education is also struggling with these problems, where students’ attitudes toward school subjects are becoming increasingly negative as they progress through their school years (Csapó, 2000). The learning environment plays a critical role in student attitudes and motivation, a situation that is equally true for out-of-school learning (OSL; see Demirci Güler & Afacan, 2013; Fägerstam & Blom, 2013).
OSL may take place in various locations, both in constructed and natural environments, where places suitable for learning methods rely on the active participation of students (e.g., museums, laboratories, zoological gardens, botanical gardens, educational trails, national parks, forests, science centers, libraries, and agricultural plants and factories). What these settings hold in common is their novelty compared with the usual classroom settings (Eshach, 2007), which can increase student motivation by breaking the monotony of the daily school environment (Dettweiler, Ünlü, Lauterbach, Becker, & Gschrey, 2015; Dettweiler, Lauterbach, Becker, & Simon, 2017; Dillon et al., 2006) and may induce memorable and long-lasting learning outcomes (James & Williams, 2017). Furthermore, physical contact offers students an opportunity for experiential learning and turns natural and cultural phenomena into real life—and thus more accessible—objects that can be experienced not only by seeing and hearing, but also by smelling, feeling, tasting, and touching (Szczepanski, Malmer, Nelson, & Dahlgren, 2007). All these qualities enrich more concrete and practical experiences, as opposed to traditional classroom lessons. A further shared advantage of OSL is their complex and varied nature, which exemplifies the interaction between different school subjects and aids knowledge transfer (Becker, Lauterbach, Spengler, Dettweiler, & Mess, 2017).
The following study presents the educational policy of OSL, the background and main aims of the research, the research design, and some results about the frequency, purpose, teaching and learning methods of out-of-school activities, as well as the opinions of stakeholders.
Case Description
The educational significance of OSL is now recognized in Hungary as evidenced by the Hungarian Government Decree 110/2012, which recommends the organization of school activities “different from traditional school lessons, such as project-based learning, forest school, museum visits, library visits, activities based on art shows or exhibitions” (Magyar Közlöny, 2012, p. 10637), provided that this does not interfere with the curriculum. The Decree specifies, however, that such activities must be free of charge for the students, and programs cannot exceed the maximum number of student contact hours per day specified by the education act.
The Core Curriculum of 2012 lists Learning How To Learn as a key area of education, with goals including the teaching of the use of “libraries and other sources of information” (110/2012, 2012, p. 10644), while the role of OSL is emphasized for the key area of Scientific Literacy in discovering and understanding our natural and man-made environment. At least one out-of-school program is expected to take place in several areas of literacy in each of the two phases of primary education (first to fourth and fifth to eighth grades) and in secondary education (ninth to 12th grades). The literacy areas for which the Core Curriculum propose out-of-school teaching are Man and Nature, Our Earth—Our Environment, Man and Society, Hungarian Language and Literature, and Art Literacy.
Naturally, OSL cannot replace classroom activities, and neither should it be seen as a rival of classroom learning; it should, instead, be considered as a complementary form of learning adding an extra dimension to education. This also means that it is more than just a leisure activity or time-off, and its educational value should be taken more seriously (Jordet, 2009; Nicol, Higgins, Ross, & Mannion, 2007). In terms of its added educational value, OSL may vary extensively; according to research findings, out-of-school programs are the most effective in learning outcomes when they are adequately planned and followed-up through regular (weekly or biweekly) or long-term activities (e.g., school camps) with explicit learning aims (Dillon et al., 2006; Nicol et al., 2007).
In our terminology, we define OSL as any class or student group activity at a location outside the school that is organized by the school, and takes place during the school term outside the walls of the school, in a natural or built environment. These activities are usually multidisciplinary by nature and may have indirect relevance to any school subjects. In terms of duration, they may involve a visit taking up a single class period, a program covering several days, or anything in between.
Overview of the Present Study
Research Goals
Hungary has not yet integrated OSL into public education, although the Core Curriculum of 2012 does include recommendations for its occasional use. Hungary also has several national parks, educational trails, zoological gardens, museums, and so on, and student labs and science centers, yet it does not have a network of outdoor learning centers that assist and complement public education, as in other countries such as Canada, Denmark, Finland, or the United Kingdom. In this complex policy and infrastructural environment, there is no clear picture of schools’ use of informal settings to teach science, which complicates efforts to further develop the practice on a large scale. In the absence of clear policy direction, principals’ attitudes toward the feasibility and educational usefulness of out-of-school programs greatly influence schools’ participation rate (for a discussion of this issue in a Danish context, cf. Bentsen, 2012). Even if the government endorses the use of OSL, personal motivation and commitment is needed to maximize its effectiveness for children’s learning (Waite, 2009). Prior research also found economic and cultural barriers to practicing OSL; some examples of these include financial costs, transportation, crowded curriculum, and lack of information (Bárd, 2009; Bentsen, Jensen, Mygind, & Randrup, 2010; Dillon et al., 2006; Nicol et al., 2007; Waite, 2009).
Research is therefore crucial to attaining a comprehensive understanding of informal science learning in different cultural contexts. The present study examined Hungarian practices related to out-of-school activities organized by schools, with questions about the frequency, aims, and methods of these programs, and questions measuring stakeholders’ opinions and attitudes toward OSL. It also explored the extent to which barriers hinder schools organizing out-of-school programs.
Method
Data collection occurred in May and June 2016. Participants included students in Grades 3 to 8, between the age of 8 and 15 (n = 4,680), their class teachers (n = 112), and school principals (n = 69), sampled from a pool of 368 institutions partnered with the Szeged Centre for Research on Learning and Instruction. Participation was voluntary with the condition that at least one class in the school participated in at least one out-of-school activity during the school term preceding data collection. An online questionnaire was administered with the eDia (Electronic Diagnostic Assessment) system via the Internet in the schools’ computer labs.
Ninety-six primary schools participated in the online survey, 44% of which were located in villages, 25% in towns, 19% in county seats, 9% in townships, 2% in municipalities, and 1% in the capital. Our sample is representative of the country for the settlement types, with independent t tests showing no significant difference between the country and the sample distributions, except in the case of schools located in the capital city, which are under-represented in the sample: t(3880) = −8.29; p < .001. Genders were distributed equally: out of 4,680 students, 2,202 were boys and 2,221 were girls (214 did not specify, and 43 marked both options, making the result non-interpretable).
Because OSL can differ from country to country (Bentsen et al., 2010), we developed and used our own instrument, based on prior Hungarian (Bárd, 2009) and international studies (Bentsen & Jensen, 2012; Bentsen et al., 2010; Dillon et al., 2006; Nicol et al., 2007; Waite, 2009). The online questionnaire was developed and validated via pilot testing in 2014 (Fűz, 2014a, 2014b). As the instrument is long and complex, only Sections II and V were used in the present study (see Appendices A and B). Statistical analyses were carried out using SPSS 22.0, where descriptive statistics and t tests were used to provide a general picture of Hungarian primary schools practicing OSL.
Selected Results
Frequency of Visits to OSL Sites
Figure 1 displays the percentages of respondents who answered “yes” to the question of whether they had visited the 10 nonschool settings with their class or group during the previous school term. The most popular places were theaters/concert halls for both subsamples. In all, 72.38% of teachers and principals thought their classes had visited a theater or concert, and 57.63% of students said they had been to theaters or concerts with their class or school group. Although the next three sites are the same for the two subsamples, they appear in different orders by frequency: library, archive (57.46%), followed by museum, art gallery (51.38%) and zoological garden, wildlife park, and sea life center (39.23%) for teachers, and zoological garden, wildlife park, sea life center (47.24%) followed by museum, art gallery (45.83%) and library and archive (44.15%) for students. The data reveal that the OSL places with the fewest mentions are laboratories and science centers.

Frequencies of respondents answering yes to visits to specific sites.
According to student answers, school classes visited one of the 10 sites 1.88 times on average (SD = 1.6) during the target period, but theaters, libraries, and museums lead the ranking in terms of visit frequency as well. The average number of the visited sites was 3.04 (SD = 1.82).
Purpose of OSL
A greater discrepancy was found between the teachers and principals’ views and the students’ views regarding the purposes of out-of-school programs (see Figure 2). Principals and teachers thought that out-of-school activities were typically organized to complement classroom teaching or, less frequently, as a part of some afterschool program, recreational activity, or annual class trip. Students, on the contrary, thought that the most frequent motivation for an out-of-school program was the annual class trip. However, if we only look at the order of purposes in terms of frequency of mention, programs complementing classroom learning come second, and those constituting a part of afterschool programs or recreational activities come third. That is, the first three positions are occupied by the same three purposes for the two subsamples, but their relative and actual frequencies differ. The ranks of field trips and student competitions as OSL programs are also the same for the two subsamples. These are the two least likely purposes among primary school students; other relatively infrequent purposes are forest schools and trips related to post-primary studies.

Purpose of OSL.
Topic of OSL
Comparing the topic rankings of the two subsamples, the data reveal three blocks; as shown in Figure 3, programs with a science topic form the highest frequency columns; this is followed by a block with topics whose ranks differ between the two subsamples but which appear with similar frequencies: literature, art, environment protection, local history, and general history. The last block comprises the least frequent topics: ethnography, career paths, lifestyle, informatics, sports, and technology.

Topics of out-of-school programs.
Teaching and Learning Methods
Principals’, teachers’, and students’ rankings show the highest level of similarity in their judgments of the dominant working methods used during out-of-school activities. Figure 4 shows that lectures and guided tours are the most frequent methods, which are followed by group work and individual work. Debates turned out to be the least frequent teaching method in out-of-school programs. Other methods, such as project-based learning, role-play and games, experiments, and competition are mentioned with moderate frequency. Interestingly, teachers see lectures and guided tours, which—from students’ perspectives—are passive learning methods, as by far the most typical activities during OSL programs, while students chose this answer only slightly more frequently than the other options. This is a positive result, as combining the frequencies of the clearly active learning methods shows more than two thirds of the methods used during OSL programs require students’ active participation. (The methods categorized as active learning methods were group work, individual work, competition, games and role-play, project-based learning, and debates. The passive methods are lectures and guided tours.)

Teaching and learning methods during OSL programs.
Student Attitudes Toward the School and Out-of-School Programs
A t test was used to examine differences between students’ attitudes toward school (M = 3.29; SD = 1.08) and toward out-of-school programs (M = 4.19; SD = 1.06). The results show significant difference, t(4281) = −47.49; p < .001, indicating that students enjoy OSL more than in-school activities.
It remains a question, however, whether this positive attitude also applies for out-of-school programs that were class-like—in other words, where the goal was not only recreation or leisure but also formal learning. Our next analysis therefore excludes programs that were organized as a class trip, reward outing, competition, or afterschool club. Out-of-school programs taking place during class trips may, of course, involve some formal learning with concrete educational goals, but the literature (Bárd, 2009; Hofstein & Rosenfeld, 1996; Tóthné Timár-Geng, 2009) suggests that these activities are often of the ad hoc type with either no educational goals or very general ones; thus, their educational relevance is low. They are therefore classed as leisure activities here, while acknowledging that learning and recreation may not be mutually exclusive in a school program (Eshach, 2007; Hofstein & Rosenfeld, 1996). OSL has its strongest learning impact, however, when the program follows a carefully designed plan and clearly articulated educational goals (Nicol et al., 2007). We therefore decided to exclude class trips. With such programs excluded, attitudes were analyzed toward the remaining programs taking place during special school days or field trips, in forest schools or with the purpose of finding out about post-primary studies. A program was included in the analysis if a given respondent chose at least one of the educational purposes listed here. If in addition to at least one educational purpose one or more noneducational (exclusion) purposes were also chosen, the program was still included. That is, the set of educational OSL places includes every place that was visited with an educational purpose regardless of whether having taken place as a part of a special school day or during a class trip.
Paired-samples t tests comparing attitudes toward school with attitudes toward the set of educational out-of-school programs still show significant differences both for the entire student sample and for the two genders separately (see Table 1). This suggests that students prefer studying outside the school to studying in the classroom even if the out-of-school program has an educational rather than just a recreational purpose.
Student Attitudes Toward School and Toward Educational Out-of-School Programs.
Examining gender differences across all out-of-school sites, girls’ attitudes were significantly more positive than boys’ both for school programs, t(4361) = −12.21; p < .001, and out-of-school programs, t(4,109, 3,987.94) = −6.73; p < .001. Figure 5 reveals that more than half of both girls and boys show a more positive attitude toward OSL than toward classroom learning, and roughly the same number of boys and girls among the group who prefer school or indicate no clear preference. Looking at the entire student sample, 61% of the total of 4,282 students, including boys and girls who gave an answer to the attitude question, rated out-of-school activities higher than classroom activities, and only 8% indicated the opposite preference.

Attitudes toward in-school and out-of-school programs.
Student, Teacher, and Principal Willingness to Participate in OSL Programs
Confirming the attitude data, Figure 6 shows a similar distribution of student answers to the question of how often they would like to participate in out-of-school programs relative to the previous school term. On the whole, students were very enthusiastic about participation, although girls were significantly more likely to want to participate in OSL than boys, t(4150) = −7.4; p < .001: 92% of girls and 86% of boys wished to visit OSL sites more frequently than they did during the previous school term. Teachers’ and principals’ responses show an even more positive picture: None of the respondents in this subsample wished to participate in OSL programs less frequently than in the previous school term, while two thirds of them wished to participate more frequently.

Wish to increase or decrease frequency of participation relative to the previous school term.
Barriers to OSL Programs
Out-of-school activities were popular among all three subsamples, but there are other factors to consider when organizing such a program. Teachers and principals were asked about five possible obstacles. Data show that by far the greatest difficulty is the issue of finding financial resources for the program (M = 1.75, SD = 0.5), but the logistical organization of a journey also poses major problems (M = 1.31, SD = 0.76). For both issues, the averages of the answers suggest that a high proportion of respondents thought that they often presented difficulties in the organization process. This is confirmed by an analysis of the data showing the percentages of respondents choosing the different ratings shown in Table 2: Only 3.5% of respondents did not consider needing to find the necessary financial resources a problem. Another obstacle is fitting the program into the school schedule or timetable (M = 0.87, SD = 0.7), but in contrast with the previous problems, the most frequent response is “sometimes” in this case.
Frequency of Barriers to the Organization of OSL.
Note. OSL = out-of-school learning.
Of the issues listed in the questionnaire, contacting the goal institution or establishment turned out to pose the least amount of difficulty (M = 0.87, SD = 0.7): Out of 167 respondents (teachers and principals), only one thought it was a frequent problem and 30 considered it to present occasional difficulty. Finding places to visit and gathering information for the trip do not appear to be problems either, with an average score less than 0.5 (M = 0.4, SD = 0.56). However, the fact that more than a third of respondents found the gathering of information an occasional problem does suggest some room for improvement among programs seeking to engage schools.
Discussion and Implications
The present study examined OSL in a Hungarian context, where OSL as a regular activity is not an integral part of the public education, but where high-quality science learning is no less important given a known decline in students’ attitudes toward school subjects. The results show several notable trends, strengths, and weaknesses in the use of OSL places by primary schools in Hungary.
Our analysis shows that participation in out-of-school programs is not treated as an integral part of primary education. Although a large proportion of students participating in the survey visited as many as two or three sites with their class during the target school term, these visits tended to be one-off occasions rather than regular events, and most of them took place as a part of an annual class trip. The occasion of OSL was found to be similar to Bárd’s (2009) results about class visits to museums: The programs were most often organized in the context of regular class trips or occurred as “reward” trips in the context of student competitions. The average number of out-of-school visits in the focal period was about 6 to 7 times, which is rather weak compared with other known countries like Scandinavian or English primary schools, where students often learn outdoors weekly or biweekly (Bentsen, 2012; Jordet, 2009; Waite, 2010). Data suggested that the locations of Hungarian OSL are primarily cultural and public institutions (theaters, museums, art galleries, libraries) and zoos or sea life centers. Green space or natural environments (parks, trails, botanical gardens, etc.) are less than 30% of destinations, in contrast with the Scandinavian context, where OSL is practiced mainly in green space (Bentsen & Jensen, 2012).
The results also show that the pattern of OSL programs conforms to the Hungarian regulations and the recommendations of the Core Curriculum. According to the data, the most frequent topics are those for which the Curriculum specifically recommends trips to OSL sites. In other countries (e.g., Denmark), OSL is not regulated by law with any greater specificity. The Danish Core Curriculum indirectly and, for some school subjects (e.g., biology, geography, physical education), directly recommends this method of learning (Bentsen, 2012) just as the Hungarian Core Curriculum does. Nevertheless, in Hungary, an out-of-school program is an exceptional event occurring only a couple of times a year and regarded as a special individual initiative. In Scandinavian countries, an increasing number of schools use OSL on a regular basis, where weekly or biweekly events are regarded as a nationwide practice (Barfod, Ejbye-Ernst, Mygind, & Bentsen, 2016; Bentsen, 2012; Bentsen et al., 2010). The fact that the Hungarian activities follow only the required minimum level confirms the importance of extended political support and public relations campaigns, which could increase the provision of OSL, as happened in Denmark (Barfod et al., 2016; Bentsen et al., 2010) and Scotland (Christie, Beames, Higgins, Nicol, & Ross, 2014). Beyond that minimum, it is up to the school, and especially the teachers, what form their OSL programs will take and with what frequency they will occur.
It is also important to look at attitudes toward OSL. Students’ attitudes toward out-of-school programs were found to be manifestly positive. The great majority of students, teachers, and principals would be pleased to participate in these programs more frequently. This suggests that the explanation for the limited occurrence of OSL does not lie in the schools’ attitudes or in negative experiences with the practice.
Principals’ and teachers’ responses suggest that the problem may lie in funding difficulties and in overcrowded timetables, similar to the situation in Scotland (Christie et al., 2014) and in other Hungarian research about school visits to museums (Bárd, 2009). This situation is especially puzzling in light of the Hungarian Government Decree (110/2012, 2012), as it specifies that out-of-school programs can only be organized by the school if they impose no costs on the students and if they do not raise the daily hours of school-related activity above the prescribed limit. The observation of these two requirements, as our results have shown, clearly presents the greatest obstacle to the organization of out-of-school programs, especially in small towns and villages where OSL is likely to involve traveling a fair distance to the site. Regular participation in out-of-school programs would be a great burden on teachers, as the school timetables would need to be rearranged every time to be able to meet the requirement of an upper limit of school hours per day. This also explains why most out-of-school programs take place as a part of the annual class trip or of afterschool programs.
Although the students’ experiences over a school term indicate that most out-of-school programs are realized during the annual class trip, the teachers and principals in the sample marked this only as the third most frequent reason. They thought that the acquisition of information related to the subject matter of a class was the most frequent purpose of visits. For the students, learning about the subject matter was the second most frequent purpose and its frequency of mention was substantially lower than for teachers/principals and lagged far behind the frequency of mentioning class trips. The discrepancy between the two subsamples may be due to the circumstance that the pedagogical purpose of a program is not necessarily explicitly known to the students, and they may regard a visit as a class trip without recognizing its relevance to a school subject. Learning may of course take place informally. Considering, however, that visits taking place during class trips were dominated by lectures and guided tours, it is more likely that the connection between the visit and the subject matter, which is so important for teachers and principals, was unnoticed by the students.
This problem could be avoided if the learning sites visited during class trips had a connection to the school subjects taught by the teachers accompanying the students on the trip, and the teachers prepared the students for the visit before the program and guided their attention during the program, making sure that the educational goals of the visit are manifest. To achieve the desired educational goals, it is also important to devote in-class time to the discussion of the experiences after the program (Eshach, 2007), when students are given an opportunity to interpret their experiences and incorporate them into their school knowledge.
Besides financial and timetable difficulties, logistics and communication may also present obstacles according to the teachers and principals in our sample. Communication with institutions and establishments offering out-of-school programs could be greatly improved by setting up OSL centers that maintain a database of available sites and programs, and offer help with logistics for interested schools, parents, and students, as is the case in countries with advanced OSL services (e.g., the United Kingdom, Denmark, and Canada). These centers could also provide information about civil and central funds, and could assist with applications for financial support. Financial difficulties could be further alleviated by making more use of natural sites in proximity to the school, such as rivers, lakes, parks, forests, educational trails, and even school grounds that provide learning opportunities not only in science topics but also other school subjects.
Because the results of our survey are concordant with the recommendations of the Core Curriculum in terms of both the frequency and the sites and themes of out-of-school programs, a revision of the Curriculum with greater emphasis on out-of-school activities would be needed to encourage an increase in both the frequency and scope of out-of-school programs meeting the expectations of primary school students, teachers, and principals. The power of education policies is evidenced, for instance, by the Scottish example where a more specific and unequivocal government policy on OSL had an immediate positive effect on educational practice, as shown by Christie et al.’s (2014) comparative study. The Curriculum for Excellence Through Outdoor Learning (Learning and Teaching Scotland, 2010) and the General Teaching Council Scotland Professional Standards (General Teaching Council Scotland, 2013) require Scottish public education to provide regular, preplanned, and good quality out-of-school experiences for every student and state that OSL must be defined as a part of formal education. Hungary could adopt a similar approach.
Limitations
The conclusions represented here must be treated with caution, as the study used a convenience sample and participation was voluntary. This method may result in selection bias; it is possible that principals and teachers who participated in the research are more open-minded to learning outside the school than others, which can skew results to show greater favorability. This may explain why teachers and principals wanted—here, anyways—to participate in more OSL programs than the students. Another reason for this difference may be that teachers and principals answered the questions according to (supposed) social expectations, even though the anonymity of all respondents was ensured by using identifier codes to log into the survey site. Furthermore, we should note that the number of teachers and school principals was substantially smaller than the size of the student subsample (see Figure 6).
On the contrary, our sampling method had the advantage of reliable respondents, who are already familiar with online educational research and who are able to participate in the research with principals, teachers, and students, despite the quite complex and long questionnaire. As no research about OSL has been conducted in Hungary yet, the results can serve as a basis for further research, hopefully with a wider and more representation sample.
Conclusion
This study modeled an extensive and time-efficient online research tool, which proved to be a useful way to gain fundamental data about OSL-practice, providing a starting point for further research. The questionnaire highlighted the overall attitudes for OSL and the interest in future out-of-classroom activities, as well as main organizational barriers. In summary, our results indicate that the students held positive attitudes toward OSL and would willingly continue to participate in similar activities in the future, as would the teachers and principals. Notwithstanding this attitude, opportunities to experience school activities outside the walls of the classroom are rare, and many of those they do attend assign a passive visitor role to them, which often carries limited educational value (Tóthné Timár-Geng, 2009). However, students are welcome to learn in such programs and this should be taken into consideration, because what “children wish to learn and enjoy learning will be better retained” (Waite, 2011. p. 67). Further research is needed to develop how to solve the main barriers of OSL and promote informal learning to a greater degree.
Footnotes
Appendix
Structure of the Educational Use of OSL Places Questionnaire–Student Version.
| Structure of the questionnaire | Number of questions | Answering categories |
|---|---|---|
| I. The administrative information of the students | 3 | Selections from determined categories |
| II. Characteristics of the specific OSL programs | 5x10 a | |
| Did you with your class/school group have a visit to . . . [location] the last school term? | Binary choice | |
| How many times did you visit this institution or establishment with your class/school group during the last term? | Text answer (with digits) | |
| What was the topic of the program/visit? | Multiple choice from determined categories (12) | |
| What was the context of the out-of-school program/visit? | Multiple choice from determined categories (9) | |
| What were the dominant methods of instruction and learning in the out-of-school program/visit? | Multiple choice from determined categories (8) | |
| III. The effect of the specific OSL programs | 15x10 a | 4-point Likert-type scale |
| IV. General Attitudes toward OSL programs (adapted from Orion & Hofstein, 1991) | 23 | 4-point Likert-type scale |
| V. Further perceptions about OSL programs | 3 | |
| Compared to the previous term, how often would you like to participate in OSL programs in the future? | Selections from determined categories (3) | |
| How much do you like school? | 5-point Likert-type scale | |
| How much do you like out-of-school programs? | 5-point Likert-type scale |
Note. The article only presents the results of highlighted questions. OSL = out-of-school learning.
The 10 OSL spaces mentioned: (1) zoo, wildlife park, sea life center; (2) botanical garden; (3) factory; (4) library; (5) laboratory; (6) museum, art gallery; (7) theater; (8) field trip, national park; (9) science center; (10) other.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The research was supported by the ÚNKP-ÚNKP-16-3 New National Excellence Program of the Ministry of Human Capacities.
