@article{sousa_alves_2006,  title={Ab initio calculation of the dynamical properties of PPP and PPV},  volume={36},  ISSN={0103-9733},  url={https://doi.org/10.1590/S0103-97332006000300072},  DOI={10.1590/S0103-97332006000300072},  number={2a},  journal={Brazilian Journal of Physics},  publisher={Sociedade Brasileira de Física},  author={Sousa, R. L. de and Alves, H. W. Leite},  year={2006},  month={Jun},  pages={501–504} }