Degtyarev, A.Kharlamov, V.2016-02-082016-02-0819971631-0713http://hdl.handle.net/11693/25670We introduce a new invariant, Pontryagin-Viro form, of real algebraic surfaces. We evaluate it for real Enriques surfaces with non-negative minimal Euler characteristic of the components of the real part and prove that, when combined with the known topological invariants, it distinguishes the deformation types of such surfaces.FrenchArticle10.1016/S0764-4442(99)80368-1