To cite package ‘gp’ in publications use:

Tsagris M (2023). gp: Maximum Likelihood Estimation of the Generalized Poisson Distribution. R package version 1.1, https://CRAN.R-project.org/package=gp.

Corresponding BibTeX entry:

  @Manual{,
    title = {gp: Maximum Likelihood Estimation of the Generalized
      Poisson Distribution},
    author = {Michail Tsagris},
    year = {2023},
    note = {R package version 1.1},
    url = {https://CRAN.R-project.org/package=gp},
  }