Abstract
References
1.
Hopkinson
G
Ley
P
. (1969 ) Brit. J. Psychiat.
115 , 917 .
2.
Mitchell-Heggs
N
. (1971 ) Proc. roy. Soc. Med.
64 , 1171 .
3.
Olds
J
. (1962 ) Physiol. Rev.
42 , 554 .
4.
Olds
M E
Olds
J
. (1963 ) J. comp. Neurol.
120 , 259 .
5.
Pollitt
J
. (1971 ) Proc. roy. Soc. Med.
64 , 1174 .
6.
Young
J Z
. (1962 ) J. ment. Sci.
108 , 119 .