@misc{indiciaec53464ba419f,
  title = {Guidelines for sample collecting and analytical methods used in the U.S. Geological Survey for determining chemical composition of coal},
  author = {Vernon Emanuel Swanson and Claude Huffman},
  year = {1976},
  doi = {10.3133/cir735},
  url = {https://pubs.usgs.gov/publication/cir735},
  note = {Source identifier: cir735}
}