@misc{indiciaefac71b804748,
  title = {A system for processing by digital computer spirograms acquired in field surveys.},
  author = {C J Derrett and C Brown},
  year = {1975},
  doi = {10.1136/thx.30.6.674},
  url = {https://pubmed.ncbi.nlm.nih.gov/1221554/},
  note = {Source identifier: 1221554}
}