Dhaliwal, R., J. Rokne, and B. M. Singh. “On Closed-Form Solutions of Triple Series Equations Involving Laguerre Polynomials”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 62, no. 2, Feb. 2010, pp. 231 -, https://umj.imath.kiev.ua/index.php/umj/article/view/2859.