1. Aumann, R. J., Integrals of set values functions, J. Math. Anal. and Appl. 12 (1965), 1–12.
2. Castaing, Ch., Sur les équations différentielles multivoques, C. R. Acad. Sc. Paris, t.263 (1966), 63–66.
3. Filippov, A. F., On certain questions in the theory of optimal control, J. SIAM Control, 1 (1962), 76–84.
4. _____, Differential equations with many-valued discontinuous right-hand side, Soviet Math. Dokl., 4 (1963), 941–945.
5. _____, Classical solutions of differential equations with multivalued right-hand side, SIAM J. Control, 5 (1967), 609–621.