1. European Pharmacopoeia, 4th edn., Council of Europe, Strasbourg, p. 926 (2002)
2. British Pharmacopoeia, 16th edn., Volume I, on line, HMSO Publication, Ltd., London, CD (2000)
3. United States Pharmacopoeia, 23rd edn., United States Pharmacopoeial Convention, Inc., Rockville, MD, USA, p. 375 (1995)