Pukalskyi, I. D. “One-Sided Nonlocal Boundary-Value Problem for Singular Parabolic Equations”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 53, no. 11, Nov. 2001, pp. 1521-32, https://umj.imath.kiev.ua/index.php/umj/article/view/4372.