January 2007 - December 2007
July 2006 - December 2006
February 2003 - June 2006
July 2000 - January 2003
January 1999 - June 2000
May 1997 - January 1999
January 1996 - April 1997
January 1995 - December 1995
July 1993 - December 1994
January 1993 - June 1993
January 1992 - December 1992
January 1991 - December 1991