1. The Extra Pharmacopoeia, Martindale, 27th Edition, p. 987.
2. United States Pharmacopoeia, 19th Edition, 1975, p. 334.
3. Isolation and Identification of Drugs, E G C Clarke, vol. 2, p. 1066.
4. The Pharmaceutical Codex, 11th Edition, p. 583.
5. Remington's Pharmaceutical Sciences, 15th Edition, 1975, p. 1043.