@article{kaplan1992,
  title={Nonparametric Estimation from Incomplete Observations},
  author={Edward L. Kaplan and Paul Meier},
  year={1992},
  journal={Springer series in statistics},
  doi={10.1007/978-1-4612-4380-9_25},
  url={https://doi.org/10.1007/978-1-4612-4380-9_25}
}