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.

Corresponding BibTeX entry:

  @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},
  }