@misc{indiciaec346eb434ac4,
  title = {Geologic characterization of natural aggregate; a field geologist's guide to natural aggregate resource assessment},
  author = {William H. Langer and Daniel H. Knepper},
  year = {1995},
  doi = {10.3133/ofr95582},
  url = {https://pubs.usgs.gov/publication/ofr95582},
  note = {Source identifier: ofr95582}
}