@misc{indiciae4e2861133663,
  title = {Slope map of the Parker quadrangle, Arapahoe and Douglas Counties, Colorado},
  author = {J. O. Maberry},
  year = {1972},
  doi = {10.3133/i770f},
  url = {https://pubs.usgs.gov/publication/i770F},
  note = {Source identifier: i770F}
}