@misc{indiciaef91997ee6b9a,
  title = {Slope map of San Mateo County, California},
  author = {R. K. Mark and E. B. Newman and E. E. Brabb},
  year = {1988},
  doi = {10.3133/i1257j},
  url = {https://pubs.usgs.gov/publication/i1257J},
  note = {Source identifier: i1257J}
}