main features vs tracing

main features

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 main features and tracing occurred in a corpus of books? (source: Google Ngram Viewer )