4BH2:
reference: Receptor binding by a ferret-transmissible H5 avian influenza virus., Xiong X, Coombs PJ, Martin SR, Liu J, Xiao H, McCauley JW, Locher K, Walker PA, Collins PJ, Kawaoka Y, Skehel JJ, Gamblin SJ, Nature. 2013 Apr 24. doi: 10.1038/nature12144. PMID: 23615615

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