Sur l'holonomie des variétés pseudo-riemanniennes de signature $(2,2+n)$

In this paper, we determinate a class of possible restricted holonomy groups for a non-irreducible indecomposable pseudo-riemannian manifold with signature $(2,2+n)$. In particular, we deduce that which associated to symmetric spaces; and give some examples of such spaces. Finally, we construct some examples of metrics whose restricted holonomy groups are not closed.