To cite gtfstools in publications use:

Herszenhut D (2021). gtfstools: General Transit Feed Specification (GTFS) Editing and Analysing Tools. doi: 10.5281/zenodo.5703285, https://doi.org/10.5281/zenodo.5703285.

Corresponding BibTeX entry:

  @Manual{,
    title = {gtfstools: General Transit Feed Specification (GTFS)
      Editing and Analysing Tools},
    author = {Daniel Herszenhut},
    month = {nov},
    year = {2021},
    publisher = {Zenodo},
    version = {v1.0.0},
    doi = {10.5281/zenodo.5703285},
    url = {https://doi.org/10.5281/zenodo.5703285},
  }