Reinforcement Learning Meets Masked Generative Models: Mask-GRPO for Text-to-Image Generation - Luo, Yifu; Hu, Xinhao; Fan, Keyu; Sun, Haoyuan; Chen, Zeyu; Xia, Bo; Zhang, Tiantian; Chang, Yongzhe; Wang, Xueqian (Advances in Neural Information Processing Systems, 2025)