Fushchich , V. I., V. A. Tychinin, and N. I. Serov. 1992. “Formula for Multiplication of Solutions of the Cortevegs—de Fries Equations”. Ukrains’kyi Matematychnyi Zhurnal 44 (5): 716-19. https://umj.imath.kiev.ua/index.php/umj/article/view/7972.