Swiss stone pine vs stone pine

Swiss stone pine

noun
  • A pine tree native to the Alps and other mountains of central and eastern Europe, Pinus cembra 

stone pine

noun
  • A species of pine native of southern Europe, Pinus pinea. 

  • Swiss stone pine (Pinus cembra) 

How often have the words Swiss stone pine and stone pine occurred in a corpus of books? (source: Google Ngram Viewer )