2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/35386I review the equivalence between duality operators on two-forms and conformal structures in four dimensions, from a Clifford algebra point of view (due to Urbantke and Harnett). I also review an application, which leads to a set of "neighbours" of Einstein's equations. An attempt to formulate reality conditions for the "neighbours" is discussed.7 pagesGeneral Relativity and Quantum Cosmologytext