microfiche vs similarity

microfiche

verb
  • To convert (documents) to microfiche format. 

noun
  • A sheet of microfilm, six by four inches, holding several hundred reduced images of document pages, read using a microfiche reader or microfilm reader. 

  • A device used to magnify and read these sheets. 

similarity

noun
  • A transformation that preserves angles and the ratios of distances 

  • The property of two matrices being similar. 

  • Closeness of appearance to something else. 

  • The relation of sharing properties. 

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