Triumph, BMW, & Kawasaki Sales Spares & Repairs.
Established for over 40 years and run by expert motorcyclists.
Fully authorised workshop.
Automobile and Motorcycle Association, Germany. Their site claims that it is the world's largest motorcycle forum.
Literature on many German marques.
Brochures and sales literature on many German marques.
motor-hist-foto.de and das-leichtmotorrad.de are the same.
das-leichtmotorrad.de FB Group Motorräder, Zeitdokumente , Fotos
Motorräder, Zeitdokumente , Fotos
Horst Mennig submitted information on a previously undocumented German marque
DKW Motorrad Club has a wealth of information, very well presented.
German translations (word only, not phrase)
by Oxford University
Not exactly an honourable mention, but a source for many early posts here which have for the most part been verified and corrected, or deleted:
German motorcycles, microcars and sidecars - JF