A space named for this mathematician is the simplest nontrivial fiber bundle of an interval over S1 (“S-one”); a quotient space description of that space is as a torus over the group action of the symmetric group on two letters. This mathematician names transformations of the complex plane with the form “az-plus-b over cz-plus-d,” as well as a function equal to zero for any number with a squared prime (10[1])factor. Attaching the edges of an Euler characteristic-zero surface named for this mathematician to itself forms the real projective plane, while joining two copies of that non-orientable surface along their boundaries creates a Klein bottle. For 10 points, twisting a piece of paper and gluing its ends together creates what German mathematician’s one-sided “strip”? ■END■