Google Books Ngram Viewer

Graph these comma-separated phrases:
case-insensitive
between and from the corpus with smoothing of .  
Search in Google Books:

1980 - 1992 1993 - 1997 1998 1999 2000 environmentally friendlier English
1980 - 1992 1993 - 1997 1998 1999 2000 more environmentally friendly English

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