@misc{indiciae67553793bb33,
  title = {Preliminary map showing global distribution of alpine-type ultramafic rocks and blueschists},
  author = {William P. Irwin and Robert G. Coleman},
  year = {1972},
  doi = {10.3133/mf340},
  url = {https://pubs.usgs.gov/publication/mf340},
  note = {Source identifier: mf340}
}