@misc{indiciae2196e191b1c0,
  title = {Normal ordering for continuum fields by functional integration within an ordered product.},
  author = {Hong-yi Fan},
  year = {1992},
  doi = {10.1103/physreva.45.6928},
  url = {https://pubmed.ncbi.nlm.nih.gov/9907826/},
  note = {Source identifier: 9907826}
}