To cite gtfs2emis in publications use:

Bazzo JP, Pereira RHM, Andrade PR (2023). “Estimating Public Transport Emissions from General Transit Feed Specification Data.” Transportation Research Part D: Transport and Environment, 119. ISSN 1361-9209, doi:10.1016/j.trd.2023.103757, https://doi.org/10.1016/j.trd.2023.103757.

Corresponding BibTeX entry:

  @Article{,
    title = {Estimating Public Transport Emissions from General Transit
      Feed Specification Data},
    author = {João Pedro Bazzo and Rafael H. M. Pereira and Pedro R.
      Andrade},
    journal = {Transportation Research Part D: Transport and
      Environment},
    year = {2023},
    volume = {119},
    doi = {10.1016/j.trd.2023.103757},
    url = {https://doi.org/10.1016/j.trd.2023.103757},
    issn = {1361-9209},
  }