@article{carvalho_chammas_cerri_2008,  title={Princípios físicos do Doppler em ultra-sonografia},  volume={38},  ISSN={0103-8478},  url={https://doi.org/10.1590/S0103-84782008000300047},  DOI={10.1590/S0103-84782008000300047},  number={3},  journal={Ciência Rural},  publisher={Universidade Federal de Santa Maria},  author={Carvalho, Cibele Figueira and Chammas, Maria Cristina and Cerri, Giovanni Guido},  year={2008},  month={May},  pages={872–879} }