VRAG-RL: Empower Vision-Perception-Based RAG for Visually Rich Information Understanding via Iterative Reasoning with Reinforcement Learning - Wang, Qiuchen; Ding, Ruixue; Zeng, Yu; Chen, Zehui; Chen, Lin; Wang, Shihang; Xie, Pengjun; Huang, Fei; Zhao, Feng (Advances in Neural Information Processing Systems, 2025)