1921-1946
Director, 1947-1957
Director, 1957-1965
Interim Director, 1965-1967
Director, 1967-1989
Acting Director, 1989
Deputy Director, 1990
Acting Director, 2008-2009
Director, 1990 - 1998
Director, 1998 - 2003
Director, 2003 - 2008
Director, 2009 - Present
