Abstract

References
1.
Gough
K R
Read
A E
Naish
J M
. (1962 ) Gut
3 , 232 .
2.
Harris
O D
Cooke
W T
. (1967 ) Brit. med. J . i , 756 .
3.
Russell
B F
. (1959 ) Proc. roy. Soc. Med . 53 , 1034 .
4.
Wells
G C
. (1962 ) Brit. med. J . ii , 937 .
5.
Wright
J T
Richardson
P C
. (1967 ) Brit. med. J . i , 540 .
