@article{santos_lópez_santos_yonamine_carmona_santos_2008,  title={Determining plasma morphine levels using GC-MS after solid phase extraction to monitor drug levels in the postoperative period},  volume={63},  ISSN={1807-5932},  url={https://doi.org/10.1590/S1807-59322008000300004},  DOI={10.1590/S1807-59322008000300004},  number={3},  journal={Clinics},  publisher={Faculdade de Medicina / USP},  author={Santos, Veronica and López, Karin Jannet Vera and Santos, Luciana Moraes and Yonamine, Mauricio and Carmona, Maria José Carvalho and Santos, Silvia Regina Cavani Jorge},  year={2008},  pages={307–314} }