2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/142343This paper has been withdrawn by the author(s), as it is superseded by 0708.2385.This paper has been withdrawn by the author(s), as it is superseded by 0708.2385AstrophysicsA centimetre-wave excess over free-free emission in planetary nebulaetext