@misc{indiciae8f8a9e1fede7,
  title = {An optical method for determining particle sizes of coarse sediment},
  author = {J.R. Ritter and E. J. Helley},
  year = {1968},
  doi = {10.3133/ofr68230},
  url = {https://pubs.usgs.gov/publication/ofr68230},
  note = {Source identifier: ofr68230}
}