@misc{indiciaeb620e9672362,
  title = {Generalized Derivatives and Approximation.},
  author = {W E Sewell},
  year = {1935},
  doi = {10.1073/pnas.21.5.255},
  url = {https://pubmed.ncbi.nlm.nih.gov/16577666/},
  note = {Source identifier: 16577666}
}