@misc{indiciae1b11bd34f50a,
  title = {The Ideas of Variable and Function.},
  author = {K Menger},
  year = {1953},
  doi = {10.1073/pnas.39.9.956},
  url = {https://pubmed.ncbi.nlm.nih.gov/16589358/},
  note = {Source identifier: 16589358}
}