@misc{indiciae625da32fd291,
  title = {Phonon Green's function.},
  author = {J Schwinger},
  year = {1991},
  doi = {10.1073/pnas.88.15.6537},
  url = {https://pubmed.ncbi.nlm.nih.gov/11607200/},
  note = {Source identifier: 11607200}
}