MarynetzV. V. “On a Mixed Problem for Systems of Definite Quasilinear Partial Differential Equations With Deviating Argument”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 46, no. 11, Nov. 1994, pp. 1581–1585, https://umj.imath.kiev.ua/index.php/umj/article/view/5600.