@misc{indiciaef63a94d44147,
  title = {A modified expiratory valve for teaching.},
  author = {A J Sansome and R Bacon},
  year = {1989},
  doi = {10.1111/j.1365-2044.1989.tb11345.x},
  url = {https://pubmed.ncbi.nlm.nih.gov/2742104/},
  note = {Source identifier: 2742104}
}