@misc{indiciae13a40349c250,
  title = {Munsell color value as related to organic carbon in Devonian shale of the Appalachian Basin},
  author = {John W. Hosterman and Sallie I. Whitlow},
  year = {1980},
  doi = {10.3133/ofr80660},
  url = {https://pubs.usgs.gov/publication/ofr80660},
  note = {Source identifier: ofr80660}
}