Nikitin, A. G. “Group Classification of Systems of Nonlinear Reaction-Diffusion Equations With Triangular Diffusion Matrix”. Ukrains’kyi Matematychnyi Zhurnal 59, no. 3 (March 25, 2007): 395–411. Accessed April 26, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3315.