struggle vs work to rule

struggle

verb
  • To strive, to labour in difficulty, to fight (for or against), to contend. 

  • To strive, or to make efforts, with a twisting, or with contortions of the body. 

noun
  • A contortion of the body in an attempt to escape or to perform a difficult task. 

  • Strife, contention, great effort. 

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 struggle and work to rule occurred in a corpus of books? (source: Google Ngram Viewer )