1. R. L. STRATONOVICH; see paper No. 21 in this symposium.
2. Asymptotic methods in the theory of non-linear oscillations (Asimptoticheskiye metody v teorii nelineinykh kolebanii);BOGOLYUBOV,1955
3. Collected works, Sobraniye trudov;ANDRONOV;Izv. Akad. Nauk SSSR,1956