Second, one can consider fiber bundles with extra structure in their fibers, and restrict attention to bundle maps which preserve this structure. This leads, for example, to the notion of a (vector) bundle homomorphism between vector bundles, in which the fibers are vector spaces, and a bundle map "φ" is required to be a linear map on each fiber. In this case, such a bundle map "φ" (covering "f") may also be viewed as a section of the vector bundle Hom("E","f*F") over "M", whose fiber over "x" is the vector space Hom("Ex","F""f"("x")) (also denoted "L"("Ex","F""f"("x"))) of linear maps from