KARSLI, Harun, and Mehmet VURAL. “On Convergence of Nonlinear Singular Integral Operators With Non-Isotropic Kernels”. Studia Universitatis Babeș-Bolyai Mathematica, vol. 60, no. 2, June 2015, pp. 267-75, https://studia.reviste.ubbcluj.ro/index.php/subbmathematica/article/view/5733.