1. Martindale: The Extra Pharmacopoeia;Reynolds,1996
2. The United States Pharmacopeia, 23rd revision, U.S. Pharmacopeial Convetion, Rockville, MD, 1995, pp. 131–145.
3. British Pharmacopoeia CD 1998, version 2, The Stationery Office Ltd., Norwich, 1998.
4. European Pharmacopoeia 1997, third edition, Convention on the Elaboration of a European Pharmacopoeia (European Treaty Series No. 50), Strasbourg, 1996, p. 345.
5. Clarke's Isolation and Identification of Drugs, 2nd edition, The Pharmaceutical Press, London, 1986, p. 140.