2OLP:
reference: Structure and Ligand Selection of Hemoglobin II from Lucina pectinata., Gavira JA, Camara-Artigas A, De Jesus-Bonilla W, Lopez-Garriga J, Lewis A, Pietri R, Yeh SR, Cadilla CL, Garcia-Ruiz JM, J Biol Chem. 2008 Apr 4;283(14):9414-23. Epub 2008 Jan 18. PMID: 18203714

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