@misc{indiciaee9c50d3bd14c,
  title = {ISOPLOT; a plotting and regression program for radiogenic-isotope data; version 2.53},
  author = {K.R. Ludwig},
  year = {1991},
  doi = {10.3133/ofr91445},
  url = {https://pubs.usgs.gov/publication/ofr91445},
  note = {Source identifier: ofr91445}
}