1. Hardman JG, Limbird LE, Molinoff PB, Ruddon RW, Gilman AG . Goodman and Gilman's. The Pharmacological Basis of Therapeutics. 9th ed pp 307–328 and pp 331–346 New York: McGraw-Hill 1996.
2. Adams A . The Welsh drug information centre. A Drug Information Bulletin Porphyria No.2 1997.
3. The Dental Practitioners Formulary pp 450 London: BDA, BMA, RPS 2000–2002.
4. Neal MJ 1 st ed pp 16–17 and pp 48–51 Medical Pharmacology at a glance Oxford: Blackwell Scientific Publications 1987.
5. Hope RA, Longmore JM, Moss PA, Warrens AN Oxford Handbook of Clinical Medicine 2 nd ed pp 656 Oxford: Oxford University Press 1989.