@misc{indiciae834aedf3197c,
  title = {Upper limits for CP 1919 X-ray emission.},
  author = {D Gruber and J L Matteson and M R Pelling and L E Peterson},
  year = {1970},
  doi = {10.1038/226532b0},
  url = {https://pubmed.ncbi.nlm.nih.gov/16057372/},
  note = {Source identifier: 16057372}
}