  In a recent paper, Akbary and Wang gave a sufficient condition for x^u + x^r
to permute GF(q), in terms of the period of a certain sequence involving sums
of cosines. As an application they gave necessary and sufficient conditions in
case u,r,q satisfy certain special properties. We show that the Akbary-Wang
sufficient condition follows from a more general sufficient condition which
does not involve sums of cosines. This leads to vastly simpler proofs of the
Akbary-Wang results, as well as generalizations to polynomials of the form
x^r*h(x^{(q-1)/d}).
