@misc{indiciae6f18073be376,
  title = {Opal claystone associated with phosphate rock in northern Saudi Arabia},
  author = {W.F. Outerbridge and C.R. Meissner},
  year = {1986},
  doi = {10.3133/ofr86103},
  url = {https://pubs.usgs.gov/publication/ofr86103},
  note = {Source identifier: ofr86103}
}