1. E. V. Babaev and N. S. Zefirov, Khim. Geterotsikl. Soedin., No. 6, 808 (1992).
2. G. R. Newkome and W. W. Paudler, Contemporary Heterocyciic Chemistry: Synthesis, Reactions and Applications, Wiley, New York (1982).
3. S. S. Nametkin, Heterocyclic Compounds [in Russian], Nauka, Moscow (1981).
4. R. M. Acheson, An Introduction to the Chemistry of Heterocyclic Compounds, Wiley, New York (1977).
5. J. A. Joule and G. F. Smith, Heterocyclic Chemistry, Van Nostrand, New York (1972).