@misc{indiciaecf969f9a92cb,
  title = {Two important invariant identities.},
  author = {Dianyan Xu},
  year = {1987},
  doi = {10.1103/physrevd.35.769},
  url = {https://pubmed.ncbi.nlm.nih.gov/9957719/},
  note = {Source identifier: 9957719}
}