authoritative vs ex cathedra

authoritative

adj
  • Having a commanding style. 

  • Arising or originating from a figure of authority 

  • Highly accurate or definitive; treated or worthy of treatment as a scholarly authority 

ex cathedra

prep
  • With authority based on one's rank or office. 

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