1. D. V. Moiseev, V. I. Goncharov, and A. V. Aksenov, Khim. Geterotsikl. Soedin., 848 (2007). [Chem. Heterocycl. Comp., 43, 715 (2007)].
2. O.N. Nadein and A. V. Aksenov, Khim. Geterotsikl. Soedin., 942 (2001). [Chem. Heterocycl. Comp., 37, 867 (2001)].
3. F. Kröhnke, H. Dickhäuser, and I. Vogt, Liebigs Ann. Chem., 644, 93 (1961).
4. S. Niementowski, Ber., 39, 385 (1906).
5. V. G. Pivovarenko and V. P. Khilya, Khim. Geterotsikl. Soedin., 625 (1991). [Chem. Heterocycl. Comp., 27, 496 (1991)].