1. Approximate methods in Quantum Mechanics;Migdal,1966
2. Asymptotic Methods in Nonlinear Mechanics;Moiseev,1969
3. Modulated oscillations and waves;Rytov;Tr. FIAN SSSR,1940
4. The method of averaging for nonsinusoidal waves;Ostrovskii;Dokl. Akad. Nauk SSSR,1970
5. On an asymptotic method in the theory of nonlinear oscillations of distributed systems;Rabinovich;Dokl. Akad. Nauk SSSR,1970