Gorunovich, V. V. “Phase Transition in an Exactly Solvable Model of Interacting Bosons”. Ukrains’kyi Matematychnyi Zhurnal 49, no. 2 (February 25, 1997): 196–205. Accessed May 19, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4997.