HHGCN-DrugRec: Hierarchical HyperGraph Convolution Network for Drug Combination Recommendation - Zihan Zhang; Hongzhi Liu; Tianqi Sun; Xiaoshuang Guo; Wu, Zhonghai (The 30th International Conference on Database Systems for Advanced Applications, DASFAA 2025, Singapore, Singapore, May 26-29, 2025, 2025)