@article{silva_toledo_vianna-soares_2017,  title={Development and validation of alternative methods by non-aqueous acid-base titration and derivative ultraviolet spectrophotometry for quantification of sildenafil in raw material and tablets},  volume={53},  ISSN={1984-8250},  url={https://doi.org/10.1590/s2175-97902017000115181},  DOI={10.1590/s2175-97902017000115181},  number={1},  journal={Brazilian Journal of Pharmaceutical Sciences},  publisher={Universidade de São Paulo, Faculdade de Ciências Farmacêuticas},  author={Silva, Taízia Dutra and Toledo, Cibele Rodrigues and Vianna-Soares, Cristina Duarte},  year={2017},  pages={e15181} }