1. Ali AA, Al-Sharabi AK, Aguirre JM, Nahas R (2004) A study of 342 oral keratotic white lesions induced by qat chewing among 2500 Yemeni. J Oral Pathol Med Off Publ Int Assoc Oral Pathol Am Acad Oral Pathol 33(6):368–372
2. Ali AA, Al-Sharabi AK, Aguirre JM (2006) Histopathological changes in oral mucosa due to takhzeen al-qat: a study of 70 biopsies. J Oral Pathol Med Off Publ Int Assoc Oral Pathol Am Acad Oral Pathol 35(2):81–85
3. IARC. Globocan database 2008. Accessed on: 09 August 2013; available at: globocan.iarc.fr. 2008
4. Al-Hebshi NN, Skaug N (2005) Khat (Catha edulis)—an updated review. Addict Biol 10(4):299–307
5. Al-Habori M (2005) The potential adverse effects of habitual use of Catha edulis (khat). Expert Opin Drug Saf 4(6):1145–1154