@article{barroso_terra_2004,  title={Beam transport in a quadrupole electrostatic system},  volume={34},  ISSN={0103-9733},  url={https://doi.org/10.1590/S0103-97332004000800017},  DOI={10.1590/S0103-97332004000800017},  number={4b},  journal={Brazilian Journal of Physics},  publisher={Sociedade Brasileira de Física},  author={Barroso, J. J. and Terra, M. O.},  year={2004},  month={Dec},  pages={1598–1601} }