@article{saab_martin-neto_2004,  title={Studies of semiquinone free radicals by ESR in the whole soil, HA, FA and humin substances},  volume={15},  ISSN={0103-5053},  url={https://doi.org/10.1590/S0103-50532004000100007},  DOI={10.1590/S0103-50532004000100007},  number={1},  journal={Journal of the Brazilian Chemical Society},  publisher={Sociedade Brasileira de Química},  author={Saab, Sérgio C and Martin-Neto, Ladislau},  year={2004},  month={Jan},  pages={34–37} }