1. Introduction to the theory of nonlinear oscillations;Butenin,1987
2. Differential equations with discontinuous right-hand sides;Filippov,1988
3. Forced oscillations in systems with discontinuous nonlinearities;Feigin,1994
4. Oscillations of nonlinear systems;Rozenvasser,1969
5. Local stability of periodic solutions in sample data control systems;Baushev;Autom. Remote Control USSR,1992