Mikitenko, E. K.; Kachkovskii, A. D.; Romanov, N. N.
Chemistry of Heterocyclic Compounds (New York, NY, United States), 1982 , vol. 18, # 4 p. 365 - 368
Khimiya Geterotsiklicheskikh Soedinenii, 1982 , vol. 18, # 4 p. 484 - 487

Upjohn Co.
Patent: US2781347 , 1955 ;