recto vs softcover

recto

noun
  • The right-hand page of a book of a script which reads from left to right, usually having an odd page number. 

  • A writ of right. 

  • The front side of a flat object which is to be examined visually, as for reading, such as a sheet, leaf, coin or medal. 

softcover

noun
  • A book having such covers. 

adj
  • Having covers made of paper or thin cardboard; paperback. 

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