@misc{Campbell21c,
  author = {Graham Campbell},
  title  = {Sub-Context-Sensitive Groups},
  year   = {2021},
  note   = {Presented at the 22nd Postgraduate Group Theory Conference ({PGTG} 2020)},
  url    = {https://cdn.gjcampbell.co.uk/2021/CS-Groups-Handouts.pdf},
}