@misc{indiciae484b74a5a9ad,
  title = {Optical method for determining particle sizes of coarse sediment},
  author = {John R. Ritter and Edward J. Helley},
  year = {1969},
  doi = {10.3133/twri05c3},
  url = {https://pubs.usgs.gov/publication/twri05C3},
  note = {Source identifier: twri05C3}
}