3D0M:
reference: Noncanonical G(syn)-G(anti) base pairs stabilized by sulphate anions in two X-ray structures of the (GUGGUCUGAUGAGGCC) RNA duplex., Rypniewski W, Adamiak DA, Milecki J, Adamiak RW, RNA. 2008 Sep;14(9):1845-51. Epub 2008 Jul 24. PMID: 18658118

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