1. ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, U.K.
2. Transducer System Division, Renishaw plc, Old Town, Wotton-under-Edge, Gloucestershire GL12 7DL, U.K.
3. Laboratoire de Cristallographie, Université de Genève, 24 quai Ernest Ansermet, CH 1211 Geneva 4, Switzerland