To cite NPCirc in publications use:

Alonso-Pena M, Oliveira M, Ameijeiras-Alonso J, Crujeiras R, Gijbels I, Rodriguez-Casal A, Scapini F (????). NPCirc: An R Package for Nonparametric Circular Methods. R package version 3.1.2. Completely revised and updated version of NPCirc with new methods and documentation., https://CRAN.R-project.org/package=NPCirc.

Oliveira M, Crujeiras R, Rodriguez-Casal A (2014). “NPCirc: An R Package for Nonparametric Circular Methods.” Journal of Statistical Software, 61(9). doi:10.18637/jss.v061.i09, https://www.jstatsoft.org/v61/i09/.

Corresponding BibTeX entries:

  @Manual{,
    title = {{NPCirc}: An {R} Package for Nonparametric Circular
      Methods},
    author = {Maria Alonso-Pena and Maria Oliveira and Jose
      Ameijeiras-Alonso and Rosa M. Crujeiras and Irene Gijbels and
      Alberto Rodriguez-Casal and Felicita Scapini},
    organization = {R package version 3.1.2},
    note = {Completely revised and updated version of NPCirc with new
      methods and documentation.},
    url = {https://CRAN.R-project.org/package=NPCirc},
  }

  @Article{,
    title = {{NPCirc}: An {R} Package for Nonparametric Circular
      Methods},
    author = {Maria Oliveira and Rosa M. Crujeiras and Alberto
      Rodriguez-Casal},
    journal = {Journal of Statistical Software},
    year = {2014},
    volume = {61},
    number = {9},
    doi = {10.18637/jss.v061.i09},
    url = {https://www.jstatsoft.org/v61/i09/},
  }