Savchenko, L. I. 1971. “On the Solution Estimation of the First Boundary Value Problem for the Quasi-Linear Systems of Differential Equations of Parabolic Type ”.
Ukrains’kyi Matematychnyi Zhurnal 23 (3): 421-28.
https://umj.imath.kiev.ua/index.php/umj/article/view/8574.