@misc{indiciae3c8bba3adf2a,
  title = {Is there a unique operator for the phase difference of two quantum fields?},
  author = {JR Torgerson and L Mandel},
  year = {1996},
  doi = {10.1103/physrevlett.76.3939},
  url = {https://pubmed.ncbi.nlm.nih.gov/10061151/},
  note = {Source identifier: 10061151}
}