@misc{indiciae48eb68d46364,
  title = {Petrology and habit of some diabase sheets in southeastern Pennsylvania},
  author = {Preston Enslow Holtz},
  year = {1949},
  doi = {10.3133/ofr4933},
  url = {https://pubs.usgs.gov/publication/ofr4933},
  note = {Source identifier: ofr4933}
}