Bondarenko, V. G. “Construction of a Fundamental Solution of a Perturbed Parabolic Equation”.
Ukrains’kyi Matematychnyi Zhurnal
, vol. 55, no. 8, Aug. 2003, pp. 1011-2,
https://umj.imath.kiev.ua/index.php/umj/article/view/3977
.