Rodríguez Sanjurjo, José Manuel2023-06-202023-06-2019890009-725Xhttps://hdl.handle.net/20.500.14352/58579Proceedings of the Winter School on Geometry and Physics (Srní, 1988).In ANR theory, the following result is well known: Suppose that X ′ is an ANR and X is a subspace of X ′ . Then X is a strong (or stationary) deformation retract of X ′ if and only if X is a deformation retract of X ′ . In this paper, a generalization of this result is obtained in Fox shape theory: Let r:U(X ′ ,P)→U(X,P) be a deformation mutational retraction. Then r is stationary if and only if r is regular, where a mutational retraction r:U(X ′ ,P)→U(X,P) is regular if for every U ′ ∈U(X ′ ,P) and for every r,r ′ ∈r with range U ′ , there is V ′ ∈U(X ′ ,P) such that r∣ ∣ V ′ ≃r ′ ∣ ∣ V ′ (rel. X ) in U ′ .engjournal articlehttp://dml.cz/bitstream/handle/10338.dmlcz/701449/WSGP_08-1988-1_21.pdfhttp://portale.unipa.it/dipartimenti/dimatematicaeinformaticahttp://dml.cz/http://math.unipa.it/~circmat/restricted access515.143MANR-spacesW-shape deformation retractFox shape theoryregular mutational retractiondeformation mutational retractionTopología1210 Topología