@article{leff_2000,  title={Tiempo de sustentabilidad},  ISSN={1414-753X},  url={https://doi.org/10.1590/S1414-753X2000000100001},  DOI={10.1590/S1414-753X2000000100001},  number={6-7},  journal={Ambiente & Sociedade},  publisher={ANPPAS - Revista Ambiente e Sociedade},  author={Leff, Enrique},  year={2000},  month={Jan},  pages={5–13} }