furthering vs recommendation

furthering

noun
  • The act by which something is furthered; furtherance. 

recommendation

noun
  • A suggestion or proposal about the best course of action (with adpositions including "about" for the context and "to" for the course of action) 

  • An act of recommending. 

  • That which is recommended. 

  • A commendation or endorsement. 

How often have the words furthering and recommendation occurred in a corpus of books? (source: Google Ngram Viewer )