opus vs publication

opus

noun
  • A work, especially of art. 

  • A work of music or set of works with a specified rank in an ordering of a composer's complete published works. 

publication

noun
  • The act of publishing printed or other matter. 

  • An issue of printed or other matter, offered for sale or distribution. 

  • The communication of information to the general public etc. 

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