SkrypnikW. I. “On Polymer Expansions for Equilibrium Systems of Oscillators With Ternary Interaction”. Ukrains’kyi Matematychnyi Zhurnal 53, no. 11 (November 25, 2001): 1532-1544. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4373.