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.

Corresponding BibTeX entry:

  @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},
  }