@misc{indiciaef30057809d28,
  title = {Census tracts, 1970, Washington urban area, D.C., MD., and VA.},
  author = {Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey},
  year = {1974},
  doi = {10.3133/i858c},
  url = {https://pubs.usgs.gov/publication/i858C},
  note = {Source identifier: i858C}
}