Helvetica Chimica Acta, , vol. 72, p. 738 - 743

Krasnov, K. A.; Slesarev, V. I.; Zakharov, A.P.; Grigor'eva, E. G.
Chemistry of Heterocyclic Compounds (New York, NY, United States), 1987 , vol. 23, # 11 p. 1218 - 1221
Khimiya Geterotsiklicheskikh Soedinenii, 1987 , # 11 p. 1523 - 1526