@misc{indiciae92405cf70819,
  title = {Group sequential procedures: calendar versus information time.},
  author = {D L Demets},
  year = {1989},
  doi = {10.1002/sim.4780081003},
  url = {https://pubmed.ncbi.nlm.nih.gov/2814068/},
  note = {Source identifier: 2814068}
}