2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/103731We exhibit several transformations of surfaces in R^4. First, one that takes a flat surface and gets a surface with flat normal bundle; then, one that takes a surface with flat normal bundle and gets a flat surface; finally, a one-parameter family of transformations on a flat surface with flat normal bundle and gives a flat surface with flat normal bundle. This family satisfies a permutability property.12 pagesDifferential Geometry53A05text