  Starting from the divergence pattern of perturbation expansions in Quantum
Field Theory and the (assumed) asymptotic character of the series, we address
the problem of ambiguity of a function determined by the perturbation
expansion. We consider functions represented by an integral of the
Laplace-Borel type along a general contour in the Borel complex plane. Proving
a modified form of the Watson lemma, we obtain a large class of functions
having the same asymptotic perturbation expansion. Some remarks on perturbative
QCD are made, using the particular case of the Adler function.
