Raiford
American Chemical Journal, 1911 , vol. 46, p. 447
Journal of the American Chemical Society, 1914 , vol. 36, p. 673

Zincke
Journal fuer Praktische Chemie (Leipzig), 1900 , vol. <2> 61, p. 566
Chemische Berichte, 1901 , vol. 34, p. 256