1. B. J. Campbell, J. S. O. Evans, F. Perselli, and H. T. Stokes, "Rietveld Refinement of Structural Distortion-Mode Amplitudes," Compcomm Newsletter, No. 8, 81-95 (2007). Published by the International Union of Crystallography, Commission on Crystallographic Computing. http://iucrcomputing.ccp14.ac.uk/iucr-top/comm/ccom/newsletters/2007nov/