To cite nprobust in publications use:

  Calonico S, Cattaneo MD, Farrell MH (2019). “nprobust: Nonparametric
  Kernel-Based Estimation and Robust Bias-Corrected Inference.”
  _Journal of Statistical Software_, *91*(8), 1-33.
  doi:10.18637/jss.v091.i08 <https://doi.org/10.18637/jss.v091.i08>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {{nprobust}: Nonparametric Kernel-Based Estimation and Robust Bias-Corrected Inference},
    author = {Sebastian Calonico and Matias D. Cattaneo and Max H. Farrell},
    journal = {Journal of Statistical Software},
    year = {2019},
    volume = {91},
    number = {8},
    pages = {1--33},
    doi = {10.18637/jss.v091.i08},
  }