cite vs retain

cite

verb
  • to summon officially or authoritatively to appear in court. 

  • to quote; to repeat, as a passage from a book, or the words of another. 

  • to list the source(s) from which one took information, words or literary or verbal context. 

noun
  • a citation 

retain

verb
  • To employ by paying a retainer. 

  • To hold back (a pupil) instead of allowing them to advance to the next class or year. 

  • To keep in one's pay or service. 

  • To keep in possession or use. 

  • To hold secure. 

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