↑ Carpenter, Paul (1990). Plants in the Landscape. New York: W.H. Freeman and Company. p. 73.
↑ Schierz, Kai Uwe (2004). "Von Bonifatius bis Beuys, oder: Vom Umgang mit heiligen Eichen". In Hardy Eidam, Marina Moritz, Gerd-Rainer Riedel, Kai-Uwe Schierz. Bonifatius: Heidenopfer, Christuskreuz, Eichenkult (in German). Stadtverwaltung Erfurt. pp. 139–45. |access-date= requires |url= (help)CS1 maint: Multiple names: editors list (link) CS1 maint: Unrecognized language (link)
