Abstract

References
1.
Ashton
N
(1950 ) Brit. J. Ophthal . 34 , 38
2.
Ashton
N
(1953 ) Brit. J. Ophthal . 37 , 282
3.
Ashton
N
(1963 ) Brit. J. Ophthal . 47 , 521
4.
Dollery
C T
Hodge
J V
Engel
M
(1962 ) Brit. med. J . ii , 1210
5.
Scott
D J
Dollery
C T
Hill
D W
Hodge
J V
Fraser
R
(1964 ) Brit. med. J . i , 811
