Google Books Ngram Viewer

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

1950 - 1978 1979 1980 - 1994 1995 - 2007 2008 center of competence English
1950 - 1982 1983 - 2002 2003 2004 - 2006 2007 - 2008 competency center English
1950 - 1980 1981 - 2000 2001 - 2002 2003 - 2004 2005 - 2008 centre of excellence English
1950 - 1994 1995 - 2005 2006 2007 2008 competence center English

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