Zelenin, K. N.; Ershov, A. Yu.
Chemistry of Heterocyclic Compounds (New York, NY, United States), 1990 , vol. 26, # 10 p. 1155 - 1158
Khimiya Geterotsiklicheskikh Soedinenii, 1990 , # 10 p. 1385 - 1388

Ershov; Gindin; Gribanov
Russian Journal of Organic Chemistry, 1997 , vol. 33, # 3 p. 388 - 391