1. Some Problems in the Theory of Non-linear Oscillations;Malkin,1956
2. The Use of the Small Parameter Method to Determine Discontinuous Periodic Solutions;Kolovskii,1961
3. Periodic solutions of piecewise-continuous systems with a small parameter;Nagayev;Prikl. Mat. Mekh.,1972
4. Differential Equations with Impulsive Actions;Samoilenko,1987
5. On the differential dependence of solutions of impulsive systems on the initial data;Akhmetov;Ukr. Mat. Zh.,1989