Mitropolsky, Yu. A., and V. N. Shevelo. “Nikolai Ivanovich Muskhelishvili (on His 80th Birthday)”. Ukrains’kyi Matematychnyi Zhurnal, vol. 23, no. 1, Dec. 1970, pp. 49-51, https://umj.imath.kiev.ua/index.php/umj/article/view/8478.