1. Conklin, Edwin Grant: Heredity and Environment in the Development of Men, ed. 5, Princeton University Press.
2. Morgan, Thomas Hunt: The Theory of the Gene, Yale University Press.
3. Eckley, William T., and Eckley, Corinne B.: Regional Anatomy of the Head and Neck, Lea Brothers & Company.
4. Macewen, William: The Growth of Bone, James Maclehouse & Sons, Glasgow.