@misc{indiciaed328eaa004d3,
  title = {Open superstrings in four dimensions.},
  author = {Z Bern and DC Dunbar},
  year = {1990},
  doi = {10.1103/physrevlett.64.827},
  url = {https://pubmed.ncbi.nlm.nih.gov/10042091/},
  note = {Source identifier: 10042091}
}