[1] Aumann J. R.: Integrals of set-valued functions. Journal of Math. Anal. and Appl. 12, 1965, pp. 1-12. DOI 10.1016/0022-247X(65)90049-1 | MR 0185073 | Zbl 0163.06301

[2] Cellina A.: Multivalued differential equations and ordinary differential equations. SIAM, Journal Appl. Math. Vol. 18, No. 2, March 1970 pp. 533-538. DOI 10.1137/0118046 | MR 0276537 | Zbl 0191.38802

[3] Kuratowski K.: Topology, vol. I. (Russian), izd. MIR, Moskva 1966. MR 0217750 | Zbl 0158.40901

[4] Olech C.: Existence of solutions of non-convex orientor fields. Difford 1974, Summer school on ordinary differential equations, Brno 1974, pp. 61 - 70. MR 0394372

[5] Sierpiński W.: Cardinal and ordinal numbers. PWN, Warszawa 1965. MR 0194339

[6] Yorke J.: Extending Liapunov's second method to non-Lipschitz Liapunov functions. Seminar on Differential Equations and ... pp. 31 - 36, Springer, Berlin, 1968. MR 0234077 | Zbl 0179.13401