MishuraYu. S., and OltsikYa. O. 1999. “Optimal Stopping Times for Solutions of Nonlinear Stochastic Differential Equations and Their Application to One Problem of Financial Mathematics”. Ukrains’kyi Matematychnyi Zhurnal 51 (6), 804–809. https://umj.imath.kiev.ua/index.php/umj/article/view/4667.