“…Researchers in numerical analysis have recently benefited from a surge of activities which overlaps with pure mathematical analysis (see, for instance, [3,6,15,16,24,26,28] and publications cited therein). Inspired by this fact and the recent works of Littlejohn and Wellman concerning the investigation of self-adjoint operators in extended Hilbert spaces (cf., e.g., [19,20,21]), in this article we consider so-called strongly continuous fractional semigroups in arbitrary normed vector spaces.…”