Gevaza, Yu. I.; Kupchik, I. P.; Staninets, V. I.
Chemistry of Heterocyclic Compounds (New York, NY, United States), 1981 , vol. 17, # 1 p. 24 - 26
Khimiya Geterotsiklicheskikh Soedinenii, 1981 , # 1 p. 32 - 34

Salkind; Chudekowa
Zhurnal Obshchei Khimii, vol. 10, p. 523,524,525
Chem. Zentralbl., 1940 , vol. 111, # II p. 1852