1ZBB:
reference: X-ray structure of a tetranucleosome and its implications for the chromatin fibre., Schalch T, Duda S, Sargent DF, Richmond TJ, Nature. 2005 Jul 7;436(7047):138-41. PMID: 16001076

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