@misc{indiciaeff30199c847b,
  title = {The difference between the potentiometric surfaces of the upper Patapsco aquifer, September 1990 and September 1997 in southern Maryland},
  author = {Stephen E. Curtin and David C. Andreasen and Frederick K. Mack},
  year = {1999},
  doi = {10.3133/ofr9986},
  url = {https://pubs.usgs.gov/publication/ofr9986},
  note = {Source identifier: ofr9986}
}