1. a Industrial Materials Group, Dept. Crystallography , Birkbeck College, University of London , Malet Street, London , WC1E 7HX , UK
2. b Daresbury Laboratory , Warrington , WA4 4AD
3. c Euroc Research AB , IDEON , Lund , Sweden
4. d Lafarge Special Cements , 730 London Rd., Grays , Essex , RM16 1UJ