Term of Office : June. 1988 ~ June. 1990
Term of Office : June. 1990 ~ September. 1993
Term of Office : September. 1993 ~ August. 1996
Term of Office : August. 1996 ~ June. 2000
Term of Office : June. 2000 ~ May. 2004
Term of Office : July. 2004 ~ June. 2008
Term of Office : August. 2008 ~ December. 2009
Term of Office : June. 2012 ~ May. 2015
Term of Office : June. 2015 ~ August. 2017
Term of Office : January. 2018 ~ January. 2021