1. International Organization for Standardization, Geneva, Switzerland, ISO Guide 35:2006
2. International Organization for Standardization, Geneva, Switzerland, ISO Guide 34:2009
3. Food and Agriculture Organization of the United Nations – Production, FAOSTAT
4. Canadian Food Inspection Agency, 2009–2010 pesticide residues and metals in dried tea, http://www.inspection.gc.ca/food/chemical-residues-microbiology/chemical-residues/dried-tea/eng/1348263667494/1348263826430 . Accessed 29 Sept 2014
5. Canadian Food Inspection Agency, 2010–2011 pesticides in coffee, fruit juice and tea, http://www.inspection.gc.ca/food/chemical-residues-microbiology/chemical-residues/pesticides/eng/1351913846907/1351913943956 . Accessed 29 Sept 2014