@misc{cvetic2016photon,
  title={Photon Spheres and Sonic Horizons in Black Holes from Supergravity and Other Theories},
  author={M. Cvetic and G. W. Gibbons and C. N. Pope},
  year={2016},
  eprint={1608.02202},
  archivePrefix={arXiv},
  primaryClass={gr-qc},
  url={https://arxiv.org/abs/1608.02202}
}