@article{MR1338319,
  title = "Extended generalized octagons and the group {${\rm He}$}",
  author = "Pasechnik, Dmitrii V.",
  year = "1995",
  issn = "0046-5755",
  journal = "Geom. Dedicata",
  mrnumber = "MR1338319 (96f:51017)",
  number = "1",
  pages = "85--101",
  volume = "56",
}