@misc{indiciae883ed778de7a,
  title = {The four functions: a conceptual analysis.},
  author = {I N Marshall},
  year = {1968},
  doi = {10.1111/j.1465-5922.1968.00001.x},
  url = {https://pubmed.ncbi.nlm.nih.gov/4866953/},
  note = {Source identifier: 4866953}
}