To cite photosearcher in publications use:

  Nathan Fox, Tom August, Francesca Mancini, Katherine E. Parks, Felix
  Eigenbrod, James M. Bullock, Louis Sutter, Laura J. Graham,
  'photosearcher' package in R: An accessible and reproducible method
  for harvesting large datasets from Flickr, SoftwareX, Volume 12,
  2020, 100624,ISSN 2352-7110,
  https://doi.org/10.1016/j.softx.2020.100624.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {'photosearcher' package in R: An accessible and reproducible method for harvesting large datasets from Flickr},
    author = {Nathan Fox and Tom August and Francesca Mancini and Katherine E. Parks and Felix Eigenbrod and James M. Bullock and Louis Sutter and Laura J. Graham},
    journal = {SoftwareX},
    year = {2020},
    volume = {12},
    number = {1},
    pages = {100624},
    url = {https://doi.org/10.1016/j.softx.2020.100624},
    doi = {10.1016/j.softx.2020.100624},
  }