BerezovskyA. A., and MitropolskiyY. A. “Problems With Free Boundaries and Nonlocal Problems for Nonlinear Parabolic Equations”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 49, no. 1, Jan. 1997, pp. 84–97, https://umj.imath.kiev.ua/index.php/umj/article/view/4988.