@article{aguiar pinto_moutinho_thomaz_2009,  title={Berry's phase in the two-level model},  volume={39},  ISSN={0103-9733},  url={https://doi.org/10.1590/S0103-97332009000300016},  DOI={10.1590/S0103-97332009000300016},  number={2},  journal={Brazilian Journal of Physics},  publisher={Sociedade Brasileira de Física},  author={Aguiar Pinto, A.C. and Moutinho, M. and Thomaz, M.T.},  year={2009},  month={Jun},  pages={326–330} }