Khachatryan , K. A., and H. S. Petrosyan. “On Bounded Solutions of a Class of Nonlinear Integral Equations on the Plane and the Urysohn Equation in a Quadrant of the Plane”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 73, no. 5, May 2021, pp. 695 -11, doi:10.37863/umzh.v73i5.6541.