To cite the spefa estimator in publications use:

  Giannini M (2025). “A spatial stochastic frontier model with fixed
  effects and endogenous environmental variables.” _Spatial Economic
  Analysis_, *20*(3), 420-441. doi:10.1080/17421772.2024.2414962
  <https://doi.org/10.1080/17421772.2024.2414962>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {A spatial stochastic frontier model with fixed effects and endogenous environmental variables},
    author = {Massimo Giannini},
    journal = {Spatial Economic Analysis},
    year = {2025},
    volume = {20},
    number = {3},
    pages = {420--441},
    doi = {10.1080/17421772.2024.2414962},
  }