Snitko, H. A. “Inverse Coefficient Problem fоr a Two-Dimensional Parabolic Equation in a domain with Free Boundary”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 68, no. 7, July 2016, pp. 972-8, https://umj.imath.kiev.ua/index.php/umj/article/view/1895.