@misc{indiciae71d16745f57f,
  title = {Some natural variations in the relative abundance of copper isotopes},
  author = {Edward C. Walker and Frank Cuttitta and F. E. Senftle},
  year = {1957},
  doi = {10.3133/tei696},
  url = {https://pubs.usgs.gov/publication/tei696},
  note = {Source identifier: tei696}
}