1. a Chemistry Department , University of Glasgow , Glasgow , G12 8QQ , Scotland
2. b Imperial Chemical Industries p.l.c., Electronics Group , Runcorn , Cheshire , WA7 4QE , England
3. c ICI Imagedata , Brantham Manningtree, Essex CO11 1NL
4. d Sri Guru Ram Rai College , Dehra Dun , India