1. A. A. Gorev, Limit Processes for a Synchronous Machine [in Russian], Gosénergoizdat, Moscow (1950).
2. P. N. Zhdanov, Stability of Electrical Systems [in Russian], Gosénergoizdat, Moscow (1948).
3. A. A. Yanko-Trinitskii, New Methods for the Analysis of the Performace of Synchronous Motions under Sharply Varying Loads [in Russian], Gosénergoizdat, Moscow (1958).
4. I. I. Blekhman, Synchrinization of Dynamical Systems [in Russian], Nauka, Moscow (1971).
5. F. Tricomi, ?Integrazione di un'equazione differenziale presentatasi in electtrotécnica,? Ann. Scuola Norm. Super. Pisa. Sci. Fis e Mat.,2, No. 2, 1?20 (1933).