@article{medeiros_figueiredo_mafra_2010,  title={Portable penetrometer for agricultural soil: sensitivity test to identify critical compaction depth},  volume={34},  ISSN={0100-0683},  url={https://doi.org/10.1590/S0100-06832010000600006},  DOI={10.1590/S0100-06832010000600006},  number={6},  journal={Revista Brasileira de Ciência do Solo},  publisher={Sociedade Brasileira de Ciência do Solo},  author={Medeiros, João Carlos and Figueiredo, Getulio Coutinho and Mafra, Álvaro Luiz},  year={2010},  month={Nov},  pages={1823–1829} }