Article Info Authors Dr.Ibraheem Mohammed Ali Al-NahellahDr.Mohammed AbdulAziz Al-MazroaDr.Abdullah Gainan Alzahrani Volume: 19 Year: 2012 Month: July Issue: 3 Pages: Reference: Al-Nahellah I., Al-Mazroa M., Alzahrani AG., .Saudi Epidemiology Bulletin. 2012;19(3):.