map on the space of differentials. A normalized isogeny is an isogeny ?: E _x001A_ E ? for which ? ? (?E ?) = ?E where ?E denotes the invariant differential of E. Algorithm 1 (identical to Algorithm 4.1 in =-=[4]-=-) evaluates, up to automorphisms of E, the unique normalized horizontal isogeny of degree ? corresponding to a given kernel ideal L ? O?. The following theorem, taken verbatim from [4], shows that the