1. P. M. Morse and H. Feshbach, Methods of Theoretical Physics [Russian translation], Vol. 1, IL, Moscow (1958).
2. Ya. A. Smorodinskii and I. I. Tugov, ?On complete sets of observables,? Preprint Joint Inst. of Nuclear Research (1965).
3. V. N. Shapovalov, V. G. Bagrov, and A. G. Meshkov, Izv. VUZ, Fiz., No. 8, 45 (1972).
4. V. N. Shapovalov, Izv. VUZ, Fiz. (in press).
5. P. J. Redmond, J. Math. Phys.,6, 1163 (1965).