referendum vs think

referendum

noun
  • An action, choice, etc., which is perceived as passing judgment on another matter. 

  • A direct popular vote on a proposed law or constitutional amendment. The adposition on is usually used before the related subject of the vote. 

think

noun
  • An act of thinking; consideration (of something). 

verb
  • To ponder, to go over in one's head. 

  • To guess; to reckon. 

  • To communicate to oneself in one's mind, to try to find a solution to a problem. 

  • To be of opinion (that); to consider, judge, regard, or look upon (something) as. 

  • To presume; to venture. 

  • To seem, to appear. 

  • To conceive of something or someone (usually followed by of; infrequently, by on). 

  • To plan; to be considering; to be of a mind (to do something). 

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