@misc{indiciae17023bf6685f,
  title = {Portable refractor unit.},
  author = {G P HALBERG},
  year = {1958},
  doi = {10.1016/0002-9394(59)90013-3},
  url = {https://pubmed.ncbi.nlm.nih.gov/13559359/},
  note = {Source identifier: 13559359}
}