Çelik, C., and N. Özarslan Tuncer. “Existence of Periodic Solution for a Tumor Growth Model With Vaccine Interaction”. Topological Methods in Nonlinear Analysis, vol. 55, no. 1, Dec. 2019, pp. 37-49, https://apcz.umk.pl/TMNA/article/view/TMNA.2019.083.