Effects of smoking cessation on the outcomes of non-surgical periodontal therapy: a systematic review and individual patient data meta-analysis - Chambrone, Leandro; Preshaw, Philip M.; Rosa, Ecinele Francisca; Heasman, Peter A.; Romito, Giuseppe Alexandre; Pannuti, Claudio Mendes; Yu-Kang, Tu (Journal of Clinical Periodontology, 2013)