1. Clark, F H. 1936. PNAS 22, 474–478.
2. Dunn, L C, Grüneberg, H, and Snell, G D. 1940. J Hered 31, 505–506.
3. Fisher, R A. 1946. Amer Nat 80, 568–578.
4. Hertwig, P. 1942. ZIAV 80, 220–246.
5. Roberts, E, and Quisenberry, J H. 1935. Amer Nat 69, 181–183.