The existence of the Boltzmann–Grad limit is proved for the solutions of the Bogolyubov
equations for a system of an infinite number of particles that interact as hard spheres. … VI
Gerasimenko, “Solutions of Bogolyubov equations for one-dimensional system of hard
spheres”, Theoret. and Math. Phys., 91:1 (1992), 410–417 …