1. Chipman, L. de V and Collins, R. J.: 1939,Canad. Med. Ass. Jour., Vol. 40, p. 557. 1939,Ab. J.A.M.A., Vol. 113, p. 716.
2. Davies, Ed. J. J. et Al.: 1928,Proc. Roy. Soc. Med., Vol. 21, p. 953.
3. Findlay, J. Parkes: 1930,Med. Jour. Aust., Vol. 1, p. 16; Vol. 2, p. 84.
4. Ketch, B.: 1937,Wien. Med. Woch., Vol. 87, p. 1211. 1938,Ab. J.A.M.A., Vol. 110, p. 476.
5. Mainland, D.: 1938,The Treatment of Clinical and Laboratory Data, Oliver and Boyd.