Gevorkyan, A.A.; Kazaryan, P.I.; Avakyan, S.V.; Simonyan, E.S. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1989 , vol. 25, # 3 p. 254 - 257 Khimiya Geterotsiklicheskikh Soedinenii, 1989 , # 3 p. 309 - 312