@article{oliveira_seifert_heine_duarte_2009,  title={Density-functional based tight-binding: an approximate DFT method},  volume={20},  ISSN={0103-5053},  url={https://doi.org/10.1590/S0103-50532009000700002},  DOI={10.1590/S0103-50532009000700002},  number={7},  journal={Journal of the Brazilian Chemical Society},  publisher={Sociedade Brasileira de Química},  author={Oliveira, Augusto F. and Seifert, Gotthard and Heine, Thomas and Duarte, Hélio A.},  year={2009},  pages={1193–1205} }