@article{Kaplan1958,
author = {Kaplan, E. and Meier, P.},
title= {Nonparametric estimation from incomplete observations},
year = {1958},
doi = {10.1080/01621459.1958.10501452},
journal = {Journal of the American Statistical Association},
volume = {53},
number = {282},
pages = {437--481},
}