@misc{indiciae21ae0eac438b,
  title = {Estimating a treatment effect under biased sampling.},
  author = {H Robbins and C H Zhang},
  year = {1988},
  doi = {10.1073/pnas.85.11.3670},
  url = {https://pubmed.ncbi.nlm.nih.gov/3375236/},
  note = {Source identifier: 3375236}
}