Nuridzhanyan,K.A.; Kuznetsova,G.V. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1972 , vol. 8, p. 1475 - 1479 Khimiya Geterotsiklicheskikh Soedinenii, 1972 , vol. 8, # 12 p. 1626 - 1631