B_K with the Wilson Quark Action: A Non-Perturbative Resolution of   Operator Mixing using Chiral Ward Identities
  We propose a non-perturbative method to determine the mixing coefficients of $\Delta s=2$ four-quark operators for the Wilson quark action using chiral Ward identities. The method is applied to calculate B_K in quenched QCD. 
JLQCD Collaboration: S. Aoki, M. Fukugita, S. Hashimoto, N. Ishizuka,   Y. Iwasaki, K. Kanaya, Y. Kuramashi, H. Mino, M. Oka...