To cite npregfast in publications use:

Sestelo M, Villanueva NM, Meira-Machado L and Roca-Pardiñas J (2017). “npregfast: An R Package for Nonparametric Estimation and Inference in Life Sciences.” Journal of Statistical Software, 82(12), pp. 1–27. doi: 10.18637/jss.v082.i12.

Corresponding BibTeX entry:

  @Article{,
    title = {{npregfast}: An {R} Package for Nonparametric Estimation
      and Inference in Life Sciences},
    author = {Marta Sestelo and Nora M. Villanueva and Luis
      Meira-Machado and Javier Roca-Pardi{\~n}as},
    journal = {Journal of Statistical Software},
    year = {2017},
    volume = {82},
    number = {12},
    pages = {1--27},
    doi = {10.18637/jss.v082.i12},
  }