@misc{indiciaed71ab4cb3f81,
  title = {Karst geology of the Upper Midwest, USA},
  author = {Daniel H. Doctor and E. Calvin Alexander},
  year = {2020},
  doi = {10.1007/978-3-030-54633-5\_1},
  url = {https://pubs.usgs.gov/publication/70217890},
  note = {Source identifier: 70217890}
}