@misc{indiciae0b64f0489da8,
  title = {Visible expiratory valves.},
  author = {T N Munro},
  year = {1989},
  doi = {10.1111/j.1365-2044.1989.tb09224.x},
  url = {https://pubmed.ncbi.nlm.nih.gov/2618999/},
  note = {Source identifier: 2618999}
}