The Rhine-Ruhr area in transformation: Towards a European metropolitan region?. European Planning Studies. 1998. Dieleman, Frans M. Randstad, Rhine-Ruhr
(页面存档备份,存于互联网档案馆) Official Website of Rhine-Ruhr S-Bahn (only German) www.marco-wegener.de - Information and History of Rhine-Ruhr-Sieg S-Bahn (German) (页面存档备份,存于互联网档案馆)