Aliouane, F., and D. Azzam-Laouir. “A Second Order Differential Inclusion With Proximal Normal Cone in Banch Spaces”. Topological Methods in Nonlinear Analysis, vol. 44, no. 1, Apr. 2016, pp. 143-60, https://apcz.umk.pl/TMNA/article/view/TMNA.2014.040.