@article{harrell2015,
  title={Regression Modeling Strategies},
  author={Frank E. Harrell and Drew Levy},
  year={2015},
  journal={Springer series in statistics},
  doi={10.1007/978-3-319-19425-7},
  url={https://doi.org/10.1007/978-3-319-19425-7}
}