sleep in vs work to rule

sleep in

verb
  • To sleep late; to go on sleeping past one's customary or planned hour. 

  • Used other than figuratively or idiomatically: see sleep, in. 

work to rule

verb
  • To work slowly by strictly following all work rules, usually in a work-to-rule job action, as part of unionized labor protest. 

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