@book{HofmannSpuler2006,
  author    = {Ernst Hofmann and Arnold Spuler},
  title     = {Die Schmetterlinge Europas, Bd. 1-3},
  edition   = {Dritte Auflage},
  url       = {http://caliban.mpiz-koeln.mpg.de/~stueber/spuler/schmetterlinge_1/index.html},
  year      = {2006},
}