@misc{indiciaec03bd39e9f7e,
  title = {A heated ultra-high-efficiency filter for mechanical ventilators.},
  author = {P Pyle and M Darlow and J E Firman},
  year = {1969},
  doi = {10.1016/s0140-6736(69)91141-6},
  url = {https://pubmed.ncbi.nlm.nih.gov/4178248/},
  note = {Source identifier: 4178248}
}