(德文) Ruhrverband data page (德文) Register of reservoirs and dams in Northrhine-Westphalia (页面存档备份,存于互联网档案馆) (德文) Private collection of pictures from the early
Substance" from the Wooden Bandkeramik Well of Erkelenz-Kückhoven (Northrhine-Westphalia, FRG). Discovery and Analysis. In: W. Brzesinski & W. Piotrowski