2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/172392O. Kobayashi in 2007 proved that differentiable mappings preserving anharmonic ratio are Moebius transformations. We strengthen his result and prove, that the requirement of differentiability and even of injectivity can be omitted.10 pagesGeometric TopologyComplex Variables30C65; 30C35text