To cite elevatr:

Hollister J, Shah T, Robitaille A, Beck M, Johnson M (2021). elevatr: Access Elevation Data from Various APIs. doi: 10.5281/zenodo.5119662, R package version 0.4.1, https://github.com/jhollist/elevatr/.

Corresponding BibTeX entry:

  @Manual{,
    author = {Jeffrey Hollister and Tarak Shah and Alec L. Robitaille
      and Marcus W. Beck and Mike Johnson},
    title = {elevatr: Access Elevation Data from Various APIs},
    year = {2021},
    note = {R package version 0.4.1},
    doi = {10.5281/zenodo.5119662},
    url = {https://github.com/jhollist/elevatr/},
  }