Mamchuev, M.O. “Boundary Value Problem for a System of Partial Differential Equations With the Dzhrbashyan–Nersesyan Fractional Differentiation Operators”. Bulletin of the Karaganda University. Mathematics Series, vol. 106, no. 2, June 2022, pp. 143-60, doi:10.31489/2022m2/143-160.