Systems of symplectic forms on four-manifolds
  We study almost Hermitian 4-manifolds with holonomy algebra, for the canonical Hermitian connection, of dimension at most one. We show how Riemannian 4-manifolds admitting five orthonormal symplectic forms fit therein and classify them. In this set-up we also fully describe almost Kaehler 4-manifolds. 
SImon G.Chiossi and Paul-Andi Nagy
math.DG