Begun, N.A. et al. 2024. Review of the research on the qualitative theory of differential equations at St. Petersburg University. II. Locally qualitative analysis of essentially nonlinear systems. Vestnik of Saint Petersburg University. Mathematics. Mechanics. Astronomy. 11, 3 (Oct. 2024), 401–418. DOI:https://doi.org/10.21638/spbu01.2024.301.