| Former (18) |
| Unofficial title | 2002 – 2006 |
| Chief Executive Officer | 1996 – 1999 |
| Unofficial title | 1972 – 1988 |
| Unofficial title | 1972 – 1991 |
| Chief Executive Officer | 2000 – 2009 |
| Unofficial title | 1972 – 1994 |
| Unofficial title | 2002 – 2006 |
| Chief Executive Officer | 1972 – 1996 |
| Unofficial title | 1972 – 1988 |
| Audit | 1972 – 1991 |
| Chief Executive Officer | 2000 – 2000 |
| Unofficial title | 1994 – 1998 |
| Management | 1972 – 1987 |
| Unofficial title | 1972 – 1988 |
| Management | 1999 – 1999 |
| Unofficial title | 1972 – 1991 |
| Unofficial title | 1994 – 2002 |
| Management | 1972 – 1993 |