Rajabov О., Mirzaev М., Yunusov Ю., Yakubov Ш., and Ismailov А. “Condition of Periodontal Tissues in Oil Refinery Workers”. Journal Problems of Biology and Medicine, no. 2 (61), May 2010, pp. 76-79, https://inlibrary.uz/index.php/problems_biology/article/view/6983.