Aachen

University Library of RWTH Aachen [free of charge]

 

Düsseldorf

University and State Library Düsseldorf (HHU) [15€ / year]

 

Cologne 

University and City Library Cologne (UOC) [20€ / year, refundable]

University Library of TH Cologne [free of charge]

 

Mainz 

University Library Mainz (JGU) [15€ / year, refundable]

 

Wuppertal  

University Library Wuppertal (BUW) [free of charge]

 

Potsdam 

University Library Potsdam (UOP) [free of charge]