Protein three-dimensional structural databases: domains, structurally aligned homologues and superfamilies. - Sowdhamini R; Burke DF; Deane C; Huang JF; Mizuguchi K; Nagarajaram HA; Overington JP; Srinivasan N; Steward RE; Blundell TL (Acta crystallographica. Section D, Biological crystallography, 1998)