standard language vs standard variety

standard language

noun
  • A language that has a standard form as one of its varieties; a language that has undergone standardization. 

  • A form of a language that is institutionally promoted, regarded as the most "correct" or neutral variety; used by a population for public and formal purposes. 

standard variety

noun
  • Synonym of standard language 

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