W.Z. Ripley, Races of Europe, pp. 58-71, Map. New York, 1898.
Ibid., p. 566. D.G. Brinton, Races and Peoples, pp. 29-30. Philadelphia, 1901.
D. Livingstone, Missionary Travels, p. 607. New York, 1858.
Williams and Calvert, Fiji and the Fijians, p. 83, New York, 1859.
P. Ehrenreich, Die Urbewohner Brasiliens, p. 32. Braunschweig, 1897.
T. Waitz, Anthropology, pp. 46-49. Edited by Collingwood, London, 1863.
Philippine Census, Vol. I, p. 552. Washington, 1903.
F. Ratzel, History of Mankind, Vol. III, p. 106. London, 1908.
Major Charles E. Woodruff, The Effect of Tropical Light on the White Man, New York, 1905, is a suggestive but not convincing discussion of the theory.
W.Z. Ripley, Races of Europe, pp. 74-77. New York, 1899.