PelyukhG. P. “On Global Solutions of Systems of Nonlinear Functional Differential Equations With Deviating Argument Dependent on Unknown Functions”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 54, no. 3, Mar. 2002, pp. 402-7, https://umj.imath.kiev.ua/index.php/umj/article/view/4076.