The Effective Prepotential of N=2 Supersymmetric SO(N_c) and Sp(N_c)   Gauge Theories
  We calculate the effective prepotentials for N=2 supersymmetric SO(N_c) and Sp(N_c) gauge theories, with an arbitrary number of hypermultiplets in the defining representation, from restrictions of the prepotentials for suitable N=2 supersymmetric gauge theories with unitary gauge groups. (This extends previous work in which the prepotential for N=2 supersymmetric SU(N_c) gauge theories was evaluated from the exact solution constructed out of spectral curves.) The prepotentials have to all orders the logarithmic singularities of the one-loop perturbative corrections, as expected from non-renormalization theorems. We evaluate explicitly the contributions of one- and two-instanton processes. 
Eric D'Hoker, I. M. Krichever and D. H. Phong