3POM:
reference: Crystal structure of the unliganded retinoblastoma protein pocket domain., Balog ER, Burke JR, Hura GL, Rubin SM, Proteins. 2011 Feb 10. doi: 10.1002/prot.23007. PMID: 21491492

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