1. Trench, R. C., "On the Study of Words", 19th ed. (London, 1886).
2. Darwin, C., "The Descent of Man" (London, 1871).
3. Baur, E., Fischer, E., and Lenz, F., "Menschliche Erblichkeitslehre" (Munich, 1923).
4. Huxley, J. S., and Haddon, A. C., "We Europeans" (London, 1935).
5. Toynbee, A. J., "A Study of History", 1 (Oxford, 1934). cf. Benedict, R., "Race and Racism" (London, 1942).