To cite gtfs2emis in publications use:

Vieira, J. P. B., Pereira, R. H. M., & Andrade, P. R. (2023). Estimating Public Transport Emissions from General Transit Feed Specification Data. Transportation Research Part D: Transport and Environment. Volume 119, 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},
  }