1. W. Glaser, Grundlagen der Elektronenoptik, Wien, Springer (1952).
2. L. D. Landau, E. M. Lifshitz, Quantum Mechanics: Non-Relativistic Theory, Vol. 3 (2nd ed.), Pergamon Press (1965).
3. H. Beitmen and G. Erdelyi, Higher Transcendental Functions. Hypergeometrical Function. Legendre Function, NewYork–Toronto–London, McGraw-Hill Book Company, Inc. (1953).
4. A. M. Bubenchikov, M. A. Bubenchikov, A. I. Potekaev, et al., Russ. Phys. J., 57, No. 8, 1126–1131 (2014).
5. J. Heading, An Introduction to Phase Integral Methods, Wiley, NY (1962).