polytechnic vs vocational university

polytechnic

adj
  • that teaches applied arts, sciences, technology, engineering and other academic subjects 

noun
  • A three-year post-secondary vocational training institute, equivalent of community college in the U.S. or TAFE in Australia. 

vocational university

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