Frigon, M., A. Granas, and Z. E.-A. Guennoun. “A Note on the Cauchy Problem for Differential Inclusions”. Topological Methods in Nonlinear Analysis, vol. 1, no. 2, June 1993, pp. 315-21, https://apcz.umk.pl/TMNA/article/view/TMNA.1993.023.