@article{gama_matos_silva_brasil_nunes_2013,  title={Potential acidity estimated by SMP pH in soils of the state of Pará},  volume={37},  ISSN={0100-0683},  url={https://doi.org/10.1590/S0100-06832013000100020},  DOI={10.1590/S0100-06832013000100020},  number={1},  journal={Revista Brasileira de Ciência do Solo},  publisher={Sociedade Brasileira de Ciência do Solo},  author={Gama, Marcos André Piedade and Matos, Gilson Sergio Bastos de and Silva, George Rodrigues da and Brasil, Edilson Carvalho and Nunes, Otiniel Ferreira},  year={2013},  month={Jan},  pages={199–203} }