To cite the mfp2 package in publications, use:

Kipruto E, Kammer M, Royston P, Sauerbrei W (2026). mfp2: Multivariable Fractional Polynomial Models with Extensions. R package version 1.1.0, https://CRAN.R-project.org/package=mfp2.

For the MFP methodology, please also cite:

Royston P, Sauerbrei W (2008). Multivariable Model-Building: A Pragmatic Approach to Regression Analysis Based on Fractional Polynomials for Modelling Continuous Variables. John Wiley & Sons, Chichester. ISBN 978-0-470-02842-1. doi:10.1002/9780470770771.

If mfpi() is used, please also cite:

Kipruto E, Royston P, Sauerbrei W (2026). “Multivariable Fractional Polynomial Interaction Models in R.” Submitted to Journal of Statistical Software.

If spike-at-zero modelling is used, please also cite:

Kipruto E, Sauerbrei W (2026). “Modelling Spike-at-Zero Covariates with Fractional Polynomials in R.” Submitted to Journal of Statistical Software.

Corresponding BibTeX entries:

  @Manual{,
    title = {{mfp2}: Multivariable Fractional Polynomial Models with
      Extensions},
    author = {Edwin Kipruto and Michael Kammer and Patrick Royston and
      Willi Sauerbrei},
    year = {2026},
    note = {R package version 1.1.0},
    url = {https://CRAN.R-project.org/package=mfp2},
  }

  @Book{,
    title = {Multivariable Model-Building: A Pragmatic Approach to
      Regression Analysis Based on Fractional Polynomials for Modelling
      Continuous Variables},
    author = {Patrick Royston and Willi Sauerbrei},
    publisher = {John Wiley & Sons},
    address = {Chichester},
    year = {2008},
    isbn = {978-0-470-02842-1},
    doi = {10.1002/9780470770771},
  }

  @Unpublished{,
    title = {Multivariable Fractional Polynomial Interaction Models in
      {R}},
    author = {Edwin Kipruto and Patrick Royston and Willi Sauerbrei},
    year = {2026},
    note = {Submitted to Journal of Statistical Software},
  }

  @Unpublished{,
    title = {Modelling Spike-at-Zero Covariates with Fractional
      Polynomials in {R}},
    author = {Edwin Kipruto and Willi Sauerbrei},
    year = {2026},
    note = {Submitted to Journal of Statistical Software},
  }