To cite npbr in publications use:

Daouia A, Laurent T, Noh H (2017). “npbr: A Package for Nonparametric Boundary Regression in R.” Journal of Statistical Software, 79(9), 1–43. doi:10.18637/jss.v079.i09.

Corresponding BibTeX entry:

  @Article{,
    title = {{npbr}: A Package for Nonparametric Boundary Regression in
      {R}},
    author = {Abdelaati Daouia and Thibault Laurent and Hohsuk Noh},
    journal = {Journal of Statistical Software},
    year = {2017},
    volume = {79},
    number = {9},
    pages = {1--43},
    doi = {10.18637/jss.v079.i09},
  }