@misc{indiciaeb50af7da0a5b,
  title = {Computer sleep stage classification using heart rate data.},
  author = {A J Welch and P C Richardson},
  year = {1973},
  doi = {10.1016/0013-4694(73)90041-2},
  url = {https://pubmed.ncbi.nlm.nih.gov/4119527/},
  note = {Source identifier: 4119527}
}