1. Al'pert, V. A. L., Gurevich, A. V., and Pitaevskii, L. P., Soviet Phys. Uspekhi, 6, 13 (1963).
2. Schiff, L. I., Quantum Mechanics (McGraw-Hill, 1955).
3. Hays, P. B., Ph. D. thesis, Univ. of Mich. 1964 (available from Univ. Microfilm Co., Ann Arbor).
4. Ginzburg, M. A., Trudy Izmiran, Akademii Nauk S.S.S.R. No. 17 (1960) (Engl. Trans. A.R.S.J., 32, 1794, 1962).
5. Kamke, E., Differential Gleichungen Lösungsmthoden and Losungen, Bd. I, Chelsea, 1948.