Waller P C, Coulson R A, Wood S M
Pharmacovigilance Assessment Group, Post-Licensing Division, Medicines Control Agency, London, UK.
Pharmacoepidemiol Drug Saf. 1996 Nov;5(6):363-75. doi: 10.1002/(SICI)1099-1557(199611)5:6<363::AID-PDS249>3.0.CO;2-7.