Hall; Howe
Journal of the Chemical Society, 1951 , p. 2480,2482

Kruglikova,R.I.; Kralinina,L.N. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1972 ,  vol. 8, p. 672 - 675Khimiya Geterotsiklicheskikh Soedinenii, 1972 ,  vol. 8, p. 743 - 747