microfiche vs source

microfiche

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. 

verb
  • To convert (documents) to microfiche format. 

source

noun
  • A reporter's informant. 

  • Source code. 

  • The name of one terminal of a field effect transistor (FET). 

  • Spring; fountainhead; wellhead; any collection of water on or under the surface of the ground in which a stream originates. 

  • The person, place, or thing from which something (information, goods, etc.) comes or is acquired. 

verb
  • To obtain or procure: used especially of a business resource. 

  • To find information about (a quotation)'s source (from which it comes): to find a citation for. 

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