@book{Darwin2006,
  author    = {Charles Darwin},
  title     = {Ch. Darwin's gesammelte Werke ; Bd. 5-7, 9,1, 9,2, 9,3, 10, 11,1, 11,2, 12,1, 12,2, 13},
  edition   = {2. Aufl. (Bd. Bd. 9,2, 11,1, 11,2); 3. Aufl. (Bd. 5-7)},
  url       = {http://caliban.mpiz-koeln.mpg.de/~stueber/darwin/werke06/index.html},
  year      = {2006},
}