@misc{berkovits2001superstrings,
  title={Superstrings in 2D Backgrounds with R-R Flux and New Extremal Black Holes},
  author={Nathan Berkovits and Sergei Gukov and Brenno Carlini Vallilo},
  year={2001},
  eprint={hep-th/0107140},
  archivePrefix={arXiv},
  primaryClass={hep-th},
  doi={10.1016/S0550-3213(01)00413-8},
  url={https://arxiv.org/abs/hep-th/0107140}
}