@article{kaplan1958,
  title={Nonparametric Estimation from Incomplete Observations},
  author={Edward L. Kaplan and Paul Meier},
  year={1958},
  journal={Journal of the American Statistical Association},
  doi={10.1080/01621459.1958.10501452},
  url={https://doi.org/10.1080/01621459.1958.10501452}
}