  A precise description of the singularities of the Borel transform of
solutions of a level-one linear differential system is deduced from a proof of
the summable-resurgence of the solutions by the perturbative method of J.
\'Ecalle. Then we compare the meromorphic classification (Stokes phenomenon)
from the viewpoint of the Stokes cocycle and the viewpoint of alien
derivatives. We make explicit the Stokes-Ramis matrices as functions of the
connection constants in the Borel plane and we develop two examples. No
assumption of genericity is made.
