Fed-GraB: Federated Long-tailed Learning with Self-Adjusting Gradient Balancer - Xiao, Zikai; Chen, Zihan; Liu, Songshang; Wang, Hualiang; FENG, YANG; Hao, Jin; Zhou, Joey Tianyi; Wu, Jian; Yang, Howard; Liu, Zuozhu (Advances in Neural Information Processing Systems, 2023)