@misc{indiciae11ee6a13f9a5,
  title = {Semi-quantitative determination of the modes of occurrence of elements in coal: Results from an international round robin project},
  author = {Jason C. Willett and Robert B. Finkelman and Stanley J. Mroczkowski and Curtis A. Palmer and Allan Kolker},
  year = {2000},
  doi = {10.3133/ofr00414},
  url = {https://pubs.usgs.gov/publication/ofr00414},
  note = {Source identifier: ofr00414}
}