To cite gtfs2emis in publications use:

Bazzo JP, Pereira RHM, Andrade PR (2022). gtfs2emis: Estimating Public Transport Emissions from GTFS Data. doi:10.31219/osf.io/8m2cy, https://doi.org/10.31219/osf.io/8m2cy.

Corresponding BibTeX entry:

  @Manual{,
    title = {gtfs2emis: Estimating Public Transport Emissions from GTFS
      Data},
    author = {João Pedro Bazzo and Rafael H. M. Pereira and Pedro R.
      Andrade},
    month = {may},
    year = {2022},
    publisher = {OSF Preprints},
    version = {v0.1.0},
    doi = {10.31219/osf.io/8m2cy},
    url = {https://doi.org/10.31219/osf.io/8m2cy},
  }