@misc{indiciae58c45294101c,
  title = {Twenty-First Annual report of the Director of the United States Geological Survey, 1899-1900: Part VI - Mineral Resources of the United States, 1899, metallic products, coal, and coke},
  author = {Charles D. Walcott},
  year = {1901},
  doi = {10.3133/ar21\_6},
  url = {https://pubs.usgs.gov/publication/ar21\_6},
  note = {Source identifier: ar21\_6}
}