4F3Z:
reference: Functional Balance of the Hemagglutinin and Neuraminidase Activities Accompanies the Emergence of the 2009 H1N1 Influenza Pandemic., Xu R, Zhu X, McBride R, Nycholat CM, Yu W, Paulson JC, Wilson IA, J Virol. 2012 Jun 20. PMID: 22718832

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