@article{oliveira_valladares_vieira_coelho_2018,  title={Availability and spatial variability of copper, iron, manganese and zinc in soils of the State of Ceará, Brazil},  volume={49},  ISSN={1806-6690},  url={https://doi.org/10.5935/1806-6690.20180042},  DOI={10.5935/1806-6690.20180042},  number={3},  journal={Revista Ciência Agronômica},  publisher={Universidade Federal do Ceará},  author={Oliveira, Mara Lucia Jacinto and Valladares, Gustavo Souza and Vieira, Johnston Silva and Coelho, Ricardo Marques},  year={2018},  month={Jul},  pages={371–380} }