4BSC:
reference: Receptor binding by an H7N9 influenza virus from humans., Xiong X, Martin SR, Haire LF, Wharton SA, Daniels RS, Bennett MS, McCauley JW, Collins PJ, Walker PA, Skehel JJ, Gamblin SJ, Nature. 2013 Jun 20. doi: 10.1038/nature12372. PMID: 23787694

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