Frankfurt vs Frankfurt an der Oder

Frankfurt

name

  • Frankfurt an der Oder, a sizable town in Brandenburg, in eastern Germany. 

  • The German financial industry. 

  • The European Central Bank. 

Frankfurt an der Oder

name

  • An independent city in Brandenburg, in eastern Germany, on the Oder River. 

How often have the words Frankfurt and Frankfurt an der Oder occurred in a corpus of books? (source: Google Ngram Viewer )