1. V. I. Arnol'd, ?On the characteristic class entering in quantization conditions,? Funkts. Anal. Prilozhen.,1, No. 1, 1?14 (1967).
2. V. I. Arnold, Ergodic Problems of Classical Mechanics, W. A. Benjamin (1968).
3. N. I. Akhiezer, Elements of the Theory of Elliptic Functions [in Russian], Nauka, Moscow (1970).
4. V. M. Babich and V. S. Buldyrev, Asymptotic Methods in Problems of the Diffraction of Short Waves. The Method of Standard Problems [in Russian], Nauka, Moscow (1972).
5. G. Bateman and A. Erdelyi, Higher Transcendental Functions [Russian translation], Nauka, Moscow (1974).