bookshelf vs bookstand

bookshelf

noun
  • A shelf or shelves for storing books for easy visual reference. 

bookstand

noun
  • A rack for holding books; a bookrack. 

  • A small stall where books are sold. 

  • A stand, made for holding books open. 

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