@misc{indiciae4b8708417d1a,
  title = {Closed strings from open bosonic strings.},
  author = {G Siopsis},
  year = {1989},
  doi = {10.1103/physrevd.39.534},
  url = {https://pubmed.ncbi.nlm.nih.gov/9959667/},
  note = {Source identifier: 9959667}
}