@article{pires_gouvêa_2004,  title={Comparing the Mori formalism and the green function methods},  volume={34},  ISSN={0103-9733},  url={https://doi.org/10.1590/S0103-97332004000600009},  DOI={10.1590/S0103-97332004000600009},  number={3b},  journal={Brazilian Journal of Physics},  publisher={Sociedade Brasileira de Física},  author={Pires, A.S.T. and Gouvêa, M.E.},  year={2004},  month={Sep},  pages={1189–1192} }