1. A. Boum, Quantum Mechanics (Mir, Moscow, 1990) [in Russian].
2. G. Hertzberg, Spectra and Structure of Diatomic Molecules (IL, Moscow, 1949) [in Russian].
3. Masataka Mizushima, The Theory of Rotating Diatomic Molecules (John Wiley and Sons, New York, Sydney, Toronto, 1975).
4. L. S. Pontryagin, Continuous Groups (Gos. Izd. Tekh.-teor. Lit., Moscow, 1954) [in Russian].
5. B. A. Dubrovin, S. P. Novikov, and A. T. Fomenko, Modern Geometry — Methods and Applications (Nauka, Moscow, 1979; Springer-Verlag, New York, 1984, 1985, 1990).