Grazulis, S., Chateigner, D., Downs, R. T., Yokochi, A.  T., Quiros,
M., Lutterotti, L., Manakova, E., Butkus, J., Moeck, P. & Le Bail, A.
(2009) "Crystallography Open Database - an open-access collection of
crystal structures". J. Appl. Cryst. 42, 726-729.