  In this paper, we show that contraction operations preserve the homology of
$n$D generalized maps, under some conditions. Removal and contraction
operations are used to propose an efficient algorithm that compute homology
generators of $n$D generalized maps. Its principle consists in simplifying a
generalized map as much as possible by using removal and contraction
operations. We obtain a generalized map having the same homology than the
initial one, while the number of cells decreased significantly.
  Keywords: $n$D Generalized Maps; Cellular Homology; Homology Generators;
Contraction and Removal Operations.
