We give a congruence for L-functions coming from affine additive exponential
sums over a finite field. Precisely, we give a congruence for certain operators
coming from Dwork's theory. This congruence is very similar to the congruence
of Manin for the characteristic polynomial of the action of Frobenius on the
Jacobian of a curve defined over a finite field.Comment: This paper generalizes and extends the results in the previous paper
arXiv:0912.205