1. B.B. Hoffman, R.J. Lofkowiz, in The Pharmacological Basis of Therapeutics, 9th edn., ed. by A.G. Gilman, J.G. Hardman, L.E. Limbird, P.B. Molinoff, R.W. Ruddon (McGraw-Hill, New York, 1996)
2. J.A. Oates, J.G. Hardman, L.E. Limbird, Goodman and Gilman’s, the Pharmacological Basis of Therapeutics, 9th edn. (McGraw-Hill, New York, 1996), p. 780
3. The United States Pharmacopoeia, The United Sates Pharmacopoeial Convention, 24th edn. (The United States Pharmacopoeia, Rockville, 2000)
4. F.B. Salem, Anal. Lett. 26(9), 1959–1966 (1993)
5. F.B. Salem, Anal. Lett. 26(2), 281–294 (1993)