Bondarenko, V. G. “Construction of a Fundamental Solution of a Perturbed Parabolic Equation”. Ukrains’kyi Matematychnyi Zhurnal 55, no. 8 (August 25, 2003): 1011–1021. Accessed April 14, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/3977.