On blowup formulae for the S-duality conjecture of Vafa and Witten II:   the universal functions
  This is the second part of two papers. In this part, we establish closed formulae for the universal functions in the blowup formulae for virtual Hodge polynomials of Gieseker moduli spaces of rank-2 stable sheaves and Uhlenbeck compactification spaces over algebraic surfaces. 
Wei-Ping Li and Zhenbo Qin