BarbulyakV. S., and KondratievYu. G. “Periodic Gibbs States”. Ukrains’kyi Matematychnyi Zhurnal 45, no. 4 (April 25, 1993): 451–458. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5831.