Petrina, E. D., & Petrina, D. Y. (1997). Existence of equilibrium states of systems of hard spheres in the Boltzmann-Enskog limit within the frame work of the grand canonical ensemble. Ukrains’kyi Matematychnyi Zhurnal, 49(1), 112–121. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/4990