The generalized Friedmann model as a self-similar solution of Vlasov–Poisson equation systemV. V. Vedenyapin, N. N. Fimin and V. M. ChechetkinEur. Phys. J. Plus, 136 6 (2021) 670DOI: https://doi.org/10.1140/epjp/s13360-021-01659-7