Kovtonyuk, D.A., I.V. Petkov, and V. I. Ryazanov. “On the Regular Solutions of the Dirichlet Problem for Beltrami Equations”. Reports of the National Academy of Sciences of Ukraine, no. 3 (March 28, 2014): 13–17. Accessed June 20, 2026. https://nasu-periodicals.org.ua/index.php/dp/article/view/15601.