@misc{indiciae1cbd3e1ad3dd,
  title = {Map showing engineering aspects of karst in the United States},
  author = {W.E. Davies and J.H. Simpson and G.C. Ohlmacher and W.S. Kirk and E.G. Newton},
  year = {1976},
  doi = {10.3133/ofr76623},
  url = {https://pubs.usgs.gov/publication/ofr76623},
  note = {Source identifier: ofr76623}
}