@misc{gukov2004index,
  title={An Index for 2D field theories with large N=4 superconformal symmetry},
  author={Sergei Gukov and Emil Martinec and Gregory Moore and Andrew Strominger},
  year={2004},
  eprint={hep-th/0404023},
  archivePrefix={arXiv},
  primaryClass={hep-th},
  url={https://arxiv.org/abs/hep-th/0404023}
}