@misc{indiciae6c084f8c0d51,
  title = {Petrology and mineralogy of alkaline rocks from the Elk massif, northeastern Poland},
  author = {T.J. Armbrustmacher and P.J. Modreski},
  year = {1994},
  doi = {10.3133/ofr94145},
  url = {https://pubs.usgs.gov/publication/ofr94145},
  note = {Source identifier: ofr94145}
}