1. M. A. Kirpichënok, S. L. Levchenko, and I. I. Grandberg, Khim. Geterotsikl. Soedin., No. 10, 1324 (1987).
2. G. Jones, W. R. Jackson, Ch. -yoo Choi, and W. R. Bergmark, J. Phys. Chem., 89, 294 (1985).
3. Yu. F. Pedash, V. F. Pedash, A. V. Luzanov, and M. I. Dzyubenko, ?The electronic structures of the excited states of the coumarin molecule in a semiempirical model,? Preprint, Institute of Radiophysics and Electronics, Academy of Sciences of the Ukrainian SSR, Kharkov, No. 84, 18 (1977).
4. M. A. Kirpichënok, L. M. Mel'nikova, L. K. Denisov, and I. I. Grandberg, Khim. Geterotsikl. Soedin., No. 4, 460 (1989).
5. A. F. Pozharskii, Theoretical Foundations of the Chemistry of Heterocycles [in Russian], Khimiya, Moscow (1985), p. 173.