Epidural butorphanol for the relief of postoperative pain.

@article{Lippmann1988EpiduralBF,
  title={Epidural butorphanol for the relief of postoperative pain.},
  author={Maurice Lippmann and Martin S. Mok},
  journal={Anesthesia and analgesia},
  year={1988},
  volume={67 4},
  pages={418}
}