Durmagambetov, Asset. “Reduction of Modern Problems of Mathematics to the Classical Riemann-Poincare-Hilbert Problem”. European Journal of Pure and Applied Mathematics 11, no. 4 (November 15, 2018): 1143–1176. Accessed July 5, 2022. https://www.ejpam.com/index.php/ejpam/article/view/3328.