%0 Journal Article %A Etayo Gordejuela, José Javier %T Non-orientable automorphisms of Riemann surfaces %D 1985 %@ 0003-889X %U https://hdl.handle.net/20.500.14352/64647 %X We study cyclic groups of automorphisms of Riemann surfaces that contain non-orientable elements. We obtain conditions for such a group, and calculate the minimum possible genus of the surface on which it acts. As a consequence of these results we obtain that the order of a sense- reversing automorphism of a Riemann surface of genus g is at most $4g+4$ for even g and 4g-4 for odd g, and that both bounds are attained for every g. %~