4XKD:
reference: Structure and Receptor Binding of the Hemagglutinin from a Human H6N1 Influenza Virus., Tzarum N, de Vries RP, Zhu X, Yu W, McBride R, Paulson JC, Wilson IA, Cell Host Microbe. 2015 Mar 11;17(3):369-76. doi: 10.1016/j.chom.2015.02.005. PMID: 25766295

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