@book{Hedwig2006,
  author    = {Johann Hedwig},
  title     = {Theoria generationis et fructificationis plantarvm cryptogamicarvm Linnaei : retractata et aucta ; c. tab. XLII coloratis},
  url       = {http://caliban.mpiz-koeln.mpg.de/~stueber/hedwig/theoria/index.html},
  year      = {2006},
}