González-Camus, J., and C. Lizama. “Globally Attractive Mild Solutions for Non-Local in Time Subdiffusion Equations of Neutral Type”. Topological Methods in Nonlinear Analysis, vol. 55, no. 1, Jan. 2020, pp. 85-103, https://apcz.umk.pl/TMNA/article/view/TMNA.2019.061.