The blowup formula for Donaldson invariants
  In this paper we present a formula which relates the Donaldson invariants of a 4-manifold X with the Donaldson invariants of its blowup X#-CP(2). This blow-up formula is independent of X and involves sigma-functions associated to a naturally arising elliptic function. This, the final version, corrects some earlier misconceptions regarding signs. 
Ronald Fintushel and Ronald Stern