We present the extension of the Einstein-Maxwell system called electrovac
universes by introducing a cosmological constant Λ. In the absence of
the Λ term, the crucial equation in solving the Einstein-Maxwell system
is the Laplace equation. The cosmological constant modifies this equation to
become in a non-linear partial differential equation which takes the form
ΔU=2ΛU3. We offer special solutions of this equation.Comment: 7 page