KnowGuard: Knowledge-Driven Abstention for Multi-Round Clinical Reasoning. - Xilin Dang; Kexin Chen 003; Xiao-Rui Su 001; Ayush Noori; Iñaki Arango; Lucas Vittor; Xinyi Long; Yuyang Du 001; Marinka Zitnik; Pheng-Ann Heng (CoRR, 2025)