@misc{indiciae117faedb0e40,
  title = {Letter: If not, why not?},
  author = {J R O'Brien},
  year = {1973},
  doi = {10.1016/s0140-6736(73)92896-1},
  url = {https://pubmed.ncbi.nlm.nih.gov/4127664/},
  note = {Source identifier: 4127664}
}