Copyright Protection for Large Language Models: A Survey of Methods, Challenges, and Trends. - Zhenhua Xu; Xubin Yue; Zhebo Wang; Qichen Liu; Xixiang Zhao; Jingxuan Zhang; Wenjun Zeng; Wengpeng Xing; Dezhang Kong; Changting Lin; Meng Han (CoRR, 2025)