@article{rosenbaum1983,
  title={The central role of the propensity score in observational studies for causal effects},
  author={Paul R. Rosenbaum and Donald B. Rubin},
  year={1983},
  journal={Biometrika},
  doi={10.1093/biomet/70.1.41},
  url={https://doi.org/10.1093/biomet/70.1.41}
}