Edmund N. Todd (1987). "A Tale of Three Cities: Electrification and the Structure of Choice in the Ruhr, 1886-1900". Social Studies of Science. 17 (3): 387–412. doi:10.1177/030631287017003001. JSTOR285130. S2CID145435566. (about Bochum, Dortmund, and Essen)
P. Krauss; E. Uetrecht, eds. (1913). "Dortmund". Meyers Deutscher Städteatlas [Meyer's Atlas of German Cities] (in German). Leipzig: Bibliographisches Institut.