O-glycosylation pattern of the SARS-CoV-2 spike protein reveals an “O-Follow-N” rule - Tian, Wenmin; Li, Delin; Zhang, Nan; Bai, Guijie; Yuan, Kai; Xiao, Haixia; Gao, Feng; Chen, Yang; Wong, Catherine C. L.; Gao, George Fu (Cell research, 2021)