Belen'kaya, I. A.; Krokhina, G. P.; Sirik, S. A.; Andronati, S. A. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1988 , vol. 24, p. 96 - 99 Khimiya Geterotsiklicheskikh Soedinenii, 1988 , vol. 24, # 1 p. 114 - 117