  We generalize and clarify Gerstenhaber and Schack's "Special Cohomology
Comparison Theorem". More specifically we obtain a fully faithful functor
between the derived categories of bimodules over a prestack over a small
category U and the derived category of bimodules over its corresponding fibered
category. In contrast to Gerstenhaber and Schack we do not have to assume that
U is a poset.
