Google Books Ngram Viewer

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

1800 - 1808 1809 - 1818 1819 - 1894 1895 - 1991 1992 - 2000 iff English
1800 - 1955 1956 - 1989 1990 - 1993 1994 - 1997 1998 - 2000 if and only if English

Run your own experiment! Raw data is available for download here.
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