1. U.S. Environmental Protection Agency, Food Quality Protection Act (FQPA) of 1996, http://www.epa.gov/pesticides/regulating/laws/fqpa/
2. U.S. Food and Drug Administration, Center for Food Safety & Applied Nutrition, Action levels for poisonous or deleterious substances in human food and animal feed, http://www.cfsan.fda.gov/list.html.
3. Codex Alimentarius Commission, FAO/WHO Food Standards, Pesticide Residues in Food, Veterinary Drug Residues in Food, Codex General Standard for Food Additives (GSFA) Online Database, http://www.codexalimentarius.net/web/index_en.jsp
4. Analytical methodology for the determination of urea: current practice and future trends
5. Analytical Methods in Wineries: Is It Time to Change?