1. Farbenfabriken Bayer & Co., German Patent 300,253 (1917).
2. “Fortschritte der Teerfarbenfabrikation.,” P.Fried-laender, Ed., 13, 360 (1917), Springer, Berlin.
3. “Beilsteins Handbuch der Organischen Chemie,” 27-1, 412 (1938), Springer, Berlin.
4. BIOS 1433, 5 (PB 81029).
5. see “The Chemistry of Synthetic Dyes and Pigments,” H. A.Lubs, Ed., Reinhold, New York, 1955, p. 692; reprint, Hafner, N. Y., 1964.