1. http://www.drugs.gov.uk
2. Patel SL Wright S Gammampila A. Home Office Online Report 47/05: Khat use among Somalis in four English cities. http://www.homeoffice.gov.uk/rds/pdfs05/rdsolr4705.pdf
3. Investigation into the toxicological effects of Catha edulis leaves;Al Mamry;a short term study in animals,2002
4. Toxicological evaluation of Catha edulis leaves;Al-Habori;a long term feeding experiment in animals,2002
5. Histological grading and staging of chronic hepatitis;Ishak;J Hepatol,1995