Pinheiro J, Bates D, R Core Team (2022). nlme: Linear and Nonlinear Mixed Effects Models. R package version 3.1-159, https://CRAN.R-project.org/package=nlme.

Pinheiro JC, Bates DM (2000). Mixed-Effects Models in S and S-PLUS. Springer, New York. doi:10.1007/b98882.

Corresponding BibTeX entries:

  @Manual{,
    title = {nlme: Linear and Nonlinear Mixed Effects Models},
    author = {José Pinheiro and Douglas Bates and {R Core Team}},
    year = {2022},
    note = {R package version 3.1-159},
    url = {https://CRAN.R-project.org/package=nlme},
  }

  @Book{,
    title = {Mixed-Effects Models in S and S-PLUS},
    author = {José C. Pinheiro and Douglas M. Bates},
    year = {2000},
    publisher = {Springer},
    address = {New York},
    doi = {10.1007/b98882},
  }