2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/15524Most of middle-aged supernova remnants (SNRs) have a distorted and complicated appearance which cannot be explained in the framework of the Sedov-Taylor model. We consider three typical examples of such SNRs (Vela SNR, MSH 15-52, G 309.2-00.6) and show that their structure could be explained as a result of interaction of a supernova (SN) blast wave with the ambient medium preprocessed by the action of the SN progenitor's wind and ionized emission.4 pages, talk given at the Gamov Memorial International Conference "The Universe of Gamow: Original Ideas in Astrophysics and Cosmology", Odessa, August 16-22, 1999; to appear in Odessa Astronomical Publications, 1999, vol. 12Astrophysicstext