1NNA:
reference: Three-dimensional structure of influenza A N9 neuraminidase and its complex with the inhibitor 2-deoxy 2,3-dehydro-N-acetyl neuraminic acid., Bossart-Whitaker P, Carson M, Babu YS, Smith CD, Laver WG, Air GM, J Mol Biol 1993 Aug 20;232(4):1069-83. PMID: 8371267

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).