@misc{indiciae35144e7f5918,
  title = {Modifications to expiratory valves.},
  author = {B E Welsh},
  year = {1990},
  doi = {10.1111/j.1365-2044.1990.tb14719.x},
  url = {https://pubmed.ncbi.nlm.nih.gov/2334049/},
  note = {Source identifier: 2334049}
}