1. T. Ważewski, “Systèmes de comande et équations au contingent,” Bull. Acad. Polon. Sci. Sér., Sci. Math. Astronom. Phys., 9, 151–155 (1961).
2. T. Ważewski, “Sur une condition équivalente à l’équation au contingent,” Bull. Acad. Polon. Sci.. Sér. Sci. Math. Astronom. Phys., 9, 865–867 (1961).
3. A. F. Fillipov, “Classical solutions of differential equations with multivalued right-hand side,” Vestn. MGU, No. 3, 16–26 (1967).
4. V. A. Plotnikov, Averaging Method in Control Problems [in Russian], Lybid’, Kiev (1992).
5. V. A. Plotnikov, A. V. Plotnikov, and A. N. Vityuk, Differential Equations with Multivalued Right-Hand Side. Asymptotic Methods [in Russian], AstroPrint, Odessa (1999).