To cite fitdistrplus in publications use:

M. L. Delignette-Muller, R. Pouillot, J.-B. Denis and C. Dutang 2014, fitdistrplus: Help to Fit of a Parametric Distribution to Non-Censored or Censored Data.

Corresponding BibTeX entry:

  @Manual{,
    title = {fitdistrplus: Help to Fit of a Parametric Distribution to
      Non-Censored or Censored Data.},
    author = {Delignette-Muller {Marie Laure} and Pouillot Regis and
      Denis Jean-Baptiste and Dutang Christophe},
    year = {2014},
    note = {R package version 1.0-3},
  }