Center-focus and isochronous center problems for discontinuous differential equations.
The authors study planar systems with a line of discontinuities. They use a geometrical proof to show a relation between the order of degeneracy of the critical point (\((m,k)\)-monodromic point) of the discontinuous differential equations and the degeneracy of the associated two smooth component differential equations.
scientific article; zbMATH DE number 1492659