Jassim, Sura, and Lekaa Ibrahim. “Correlation Between Periodontal Health Status and Salivary Matrix Metalloproteinase-9 Levels in Smoker and Non-Smoker Chronic Periodontitis Patients (A Comparative Study) ”. Journal of Baghdad College of Dentistry 28, no. 4 (December 14, 2016): 128-133. Accessed November 20, 2019. http://jbcd.uobaghdad.edu.iq/index.php/jbcd/article/view/1511.