To cite NPCirc in publications use:

Jose Ameijeiras-Alonso, Rosa M. Crujeiras, Alberto Rodriguez-Casal (2018). multimode: An R Package for Mode Assessment. arXiv preprint arXiv: 1803.00472.

Corresponding BibTeX entry:

  @Article{,
    title = {multimode: An {R} Package for Mode Assessment},
    author = {Jose Ameijeiras-Alonso and Rosa M. Crujeiras and Alberto
      Rodr{\'i}guez-Casal},
    journal = {arXiv preprint arXiv: 1803.00472},
    year = {2018},
    url = {https://arxiv.org/abs/1803.00472},
  }