© Owned by the authors, published by EDP Sciences, 2010.The serious inconsistency problem between the values of experimental and theoretical Γn/Γp ratio of the nonmesonic weak decay of Λ hypernuclei has been resolved recently. We have shown that the reason behind the problem was the quenching of the nucleon yields which in turn was due to the contribution of the three-body process. We have measured that the branching ratio of the three-body process in nonmesonic weak decay, 0.29±0.13, is so large that the absolute values of Γn and Γp must be determined taking account of the contribution of the 3-body process. In this paper, the recent studies toward the finding of the 3-body process via the exclusive coincidence experiments are presented.