We show that the normal connected sum of two minimal symplectic 4-manifolds (neither of them rational or ruled) is a minimal symplectic 4-manifold. In the proof we use a symplectic sum formula for Gromov-Witten invariants.
LI, TIAN-JUN and STIPSICZ, ANDRAS I. (2002) "Minimality of certain normal connected sums," Turkish Journal of Mathematics: Vol. 26: No. 1, Article 5. Available at: https://journals.tubitak.gov.tr/math/vol26/iss1/5