The Bomber's Baedeker : (guide to the economic importance of German towns and cities) : 2. Lahr - Zwickau. London. London : Enemy Branch (Foreign Office & Ministry of Economic Warfare): [1944]. Universitätsbibliothek Mainz, https://nbn-resolving.org/urn:nbn:de:hebis:77-vcol-20184 / Public Domain Mark 1.0