To cite sfa in publications use:

  David H. Bernstein, Christopher F. Parmeter, and Alexander D Stead
  (2026). Stochastic Froniter Analysis: The sfa Package. Working Paper.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Stochastic Frontier Analysis: The sfa Package},
    author = {{David H. Bernstein} and {Christopher F. Parmeter} and {Alexander D. Stead}},
    journal = {Working Paper},
    year = {2026},
  }