H. Bruin, THE EXISTENCE OF ABSOLUTELY CONTINUOUS INVARIANT-MEASURES IS NOT A TOPOLOGICAL INVARIANT FOR UNIMODAL MAPS, Ergodic theory & dynamical systems, 18, 1998, pp. 555-565
Within the class of S-unimodal maps with fixed critical order it is sh
own that the existence of an absolutely continuous invariant probabili
ty measure is not a topological invariant.