  @Manual{medicalriskpkg,
    title = {medicalrisk: Medical Risk and Comorbidity Tools for ICD-9-CM Data},
    author = {Patrick McCormick and Thomas Joseph},
    year = {2016},
    note = {R package version 12},
    url = {https://CRAN.R-project.org/package=medicalrisk}
  }

  @Article{comorbiditypkg,
    author = {Alessandro Gasparini},
    title = {Comorbidity: An R Package for Computing Comorbidity Scores},
    journal = {Journal of Open Source Software},
    year = {2018},
    volume = {3},
    issue = {23},
    pages = {648},
    doi = {10.21105/joss.00648},
    url = {https://doi.org/10.21105/joss.00648},
  }

  @Manual{R_2018,
    title = {R: A Language and Environment for Statistical Computing},
    author = {{R Core Team}},
    organization = {R Foundation for Statistical Computing},
    address = {Vienna, Austria},
    year = {2018},
    url = {https://www.R-project.org/},
  }

  @MISC{eigenweb,
    author = {Gael Guennebaud and Benoit Jacob and others},
    title = {Eigen v3, A C++ Template Library for Linear Algebra: Matrices, Vectors, Numerical Solvers, and Related Algorithms.},
    version = {3},
    howpublished = {http://eigen.tuxfamily.org},
    year = {2010},
    note = {Online; accessed 5-May-2018}
  }
