1. Stats and facts http://www.justice.gov/dea/statistics
2. Technical article: cocaine residues on money;Aaron;Crime Laboratory Digest,1987
3. Analysis of currency for cocaine contamination;Hudson;Canadian Society of Forensic Science Journal,1989
4. U.S. v. U.S. Currency (Alexander) United States Court of Appeals, Ninth Circuit 1994
5. Drug contamination of US paper currency;Jenkins;Forensic Sci Int,2001