Putonghua vs Zhongwen

Putonghua

name
  • Standard Mandarin, the official language of the People's Republic of China; the state-designated national speech of the Han nationality using Beijing pronunciation as the standard pronunciation, Beijing speech as the basic dialect, and the model writing of the modern vernacular prose as the norm for grammar. 

Zhongwen

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