PavlenkoV. N., and FedyashevM. S. 2012. “Periodic Solutions of a Parabolic Equation With Homogeneous Dirichlet Boundary Condition and Linearly Increasing Discontinuous Nonlinearity”. Ukrains’kyi Matematychnyi Zhurnal 64 (8), 1080-88. https://umj.imath.kiev.ua/index.php/umj/article/view/2642.