canonical form vs citation form

canonical form

noun
  • Synonym of dictionary form 

  • A standard or normal presentation of a mathematical entity or a text string, etc. 

  • Any of a set of representations of the resonance structure of a molecule each of which contributes to the real structure; a contributing structure. 

citation form

noun
  • The basic form of a word used as a dictionary headword. 

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