Voir la notice de l'article provenant de la source European Digital Mathematics Library
@article{PORMA_1979__38_3-4_115385, author = {Levi, Sandro}, title = {Closed mappings are open at a $G_\delta $ set}, journal = {Portugaliae mathematica}, pages = {7--9}, publisher = {mathdoc}, volume = {38}, number = {3-4}, year = {1979}, mrnumber = {0745228}, zbl = {0524.54009}, language = {en}, url = {http://geodesic.mathdoc.fr/item/PORMA_1979__38_3-4_115385/} }
Levi, Sandro. Closed mappings are open at a $G_\delta $ set. Portugaliae mathematica, Tome 38 (1979) no. 3-4, pp. 7-9. http://geodesic.mathdoc.fr/item/PORMA_1979__38_3-4_115385/