@article{shaju_2010,  title={Smoking as a risk factor for periodontitis: a literature review},  volume={25},  ISSN={1980-6523},  url={https://doi.org/10.1590/S1980-65232010000400016},  DOI={10.1590/S1980-65232010000400016},  number={4},  journal={Revista Odonto Ciência},  publisher={Pontifícia Universidade Católica do Rio Grande do Sul},  author={Shaju, Jacob P},  year={2010},  month={Dec},  pages={406–411} }