microfiche vs tracing

microfiche

noun
  • A device used to magnify and read these sheets. 

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

verb
  • To convert (documents) to microfiche format. 

tracing

noun
  • A record in the form of a graph made by a device such as a seismograph. 

  • The process of finding something that is lost by studying evidence. 

  • A regular path or track; a course. 

  • The reproduction of an image made by copying it through translucent paper. 

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