Schäfer, Sir E.A. Endocrine Glands and Internal Secretions. Stanford University, 1914, p. 91.
Paton, D. Noël. Regulators of Metabolism. London, 1913, p. 146.
Weininger, Otto. Sex and Character. London & N.Y., 1906. Eng. trans. of Geschlecht u. Charakter, Vienna & Leipzig, 1901 & 1903.