Liu, Yu, et al. “OPERA: A Reinforcement Learning--Enhanced Orchestrated Planner-Executor Architecture for Reasoning-Oriented Multi-Hop Retrieval”. Proceedings of the AAAI Conference on Artificial Intelligence, vol. 40, no. 38, Mar. 2026, pp. 32258-66, doi:10.1609/aaai.v40i38.40499.