@article{roberto_silva_caldas_viana_2004,  title={Non-twist field line mappings for tokamaks with reversed magnetic shear},  volume={34},  ISSN={0103-9733},  url={https://doi.org/10.1590/S0103-97332004000800046},  DOI={10.1590/S0103-97332004000800046},  number={4b},  journal={Brazilian Journal of Physics},  publisher={Sociedade Brasileira de Física},  author={Roberto, M. and Silva, E. C. da and Caldas, I. L. and Viana, R. L.},  year={2004},  month={Dec},  pages={1759–1765} }