Authors: Pavel V Afonine; Ralf W Grosse-Kunstleve; Nathaniel Echols; Jeffrey J Headd; Nigel W Moriarty; Marat Mustyakimov; Thomas C Terwilliger; Alexandre Urzhumtsev; Peter H Zwart; Paul D Adams Journal: Acta Crystallogr D Biol Crystallogr Date: 2012-03-16