@article{lenza_vasconcelos_2001,  title={Preparation of silica by sol-gel method using formamide},  volume={4},  ISSN={1516-1439},  url={https://doi.org/10.1590/S1516-14392001000300008},  DOI={10.1590/S1516-14392001000300008},  number={3},  journal={Materials Research},  publisher={ABM, ABC, ABPol},  author={Lenza, R.F.S. and Vasconcelos, W.L.},  year={2001},  month={Jul},  pages={189–194} }