Wang, J., Y. Zhou, and W. Wei. “Impulsive Problems for Fractional Evolution Equations and Optimal Controls in Infinite Dimensional Spaces”. Topological Methods in Nonlinear Analysis, vol. 38, no. 1, Apr. 2011, pp. 17-43, https://apcz.umk.pl/TMNA/article/view/TMNA.2011.022.