2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/157194A new invariant, the Pontrjagin-Viro form, of algebraic surfaces is introduced and studied. It is related to various Rokhlin-Guillou-Marin forms and generalizes Mikhalkin's complex separation. The form is calculated for all real Enriques surfaces for which it is well defined.AMSTeX with amsppt and epsf.tex, 24 pages with 4 figuresAlgebraic Geometry57S25, 14J28, 14P25text