@misc{indiciae6c14858764ad,
  title = {Map of the United States showing distances from urban areas having populations greater than 2,500},
  author = {Jack Burton Epstein},
  year = {1981},
  doi = {10.3133/ofr81157},
  url = {https://pubs.usgs.gov/publication/ofr81157},
  note = {Source identifier: ofr81157}
}