Mitigating Reward Over-optimization in Direct Alignment Algorithms with Importance Sampling - Phuc, Nguyen; Nguyen, Ngoc-Hieu; M. H. Nguyen, Duy; Liu, Anji; Mai, An; Nguyen, Thanh Binh; Sonntag, Daniel; Doan, Khoa D (Advances in Neural Information Processing Systems, 2025)