Abstract
References
1.
Redhead
I H
. (1960 ) Brit. med. J.
i , 695 .
2.
Reid
J J A
. (1960 ) Med. Offr.
103 , 325 .
3.
Walker
J B
. (1959 ) Postgrad. med. J.
35 , 302 .
4.
Wilkerson
H L C
Krall
L P
. (1947 ) J. Amer. med. Ass.
135 , 209 .