Abstract

References
1.
Cohen
B.
(1959 ) Brit. dent. J. , 107 , 31 .
2.
Fish
E. W.
(1935 ) Brit. dent. J. , 58 , 531 .
3.
Rushton
M. A.
(1951 ) Brit. dent. J. , 90 , 87 .
4.
Skillen
W. G.
(1930 ) J. Amer. dent. Ass. , 17 , 645 .
