I read the paper “Hard and Easy Problems for Supersingular Isogeny Graphs” from C.Petit and K.Lauter. There is a statement that says that any smooth degree endomorphism of a supersingular elliptic curve can be efficiently represented as a composition of small degree isogenies.
Is there any reference to look up how this work: how to efficiently represent a smooth degree endomorphism as a composition of small degree isogenies?