  This note is an appendix to a preprint by E. Hellmann. We give a complete
classification of simple objects of the category of vector spaces D over K =
Fpbar((u)) equipped with an endomorphism phi whose image generates D and that
are semi-linear with respect to the ring morphism sending u to u^b (b > 1 is an
integer) and acting on elements of k through a fixed automorphism. Some of
these phi-modules are involved in the classification of finite flat group
schemes over ring of integers of p-adic fields.
