@misc{indiciaec435b13dfa6c,
  title = {Heterotic string in an arbitrary background field.},
  author = {A Sen},
  year = {1985},
  doi = {10.1103/physrevd.32.2102},
  url = {https://pubmed.ncbi.nlm.nih.gov/9956387/},
  note = {Source identifier: 9956387}
}