Abstract

References
1.
Apley
J
. (1953 ) Arch. Dis. Child.
28 , 423 .
2.
Pracy
R
. (1965 ) Proc. roy. Soc. Med.
58 , 267 .
3.
Wilson
T G
. (1952 ) Proc. roy. Soc. Med.
45 , 355 .
