Kalenyuk P. I., and Nitrebich Z. M. “A Scheme of Variable Separation for Matrix Bilinear Functional Equation and Its Use”. Ukrains’kyi Matematychnyi Zhurnal 44, no. 9 (October 7, 1992): 1201-1209. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/8170.