1. Avetisyan, A.A., Aleksanyan, I.L., and Alvandzhyan, A.G., Khim. Geterotsikl. Soedin., 1996, p. 909.
2. Avetisyan, A.A., Aleksanyan, I.L., and Alvandzhyan, A.G., Khim. Geterotsikl. Soedin., 1996, p. 1002.
3. Avetisyan, A.A., Aleksanyan, I.L., and Alvandzhyan, A.G., Khim. Geterotsikl. Soedin., 1997, p. 48.
4. Shah, V.R., Bose, J.L., and Shah, R.C., J. Org. Chem., 1960, vol. 25, p. 677.
5. Clayton, B.A. and Colden, W.I., J. Chem. Soc., 1912, vol. 101, p. 210.