2006 - present ............................................. ⊕ 1998 - 2006 ................................................. ⊕ 1997 - 1998 ................................................. ⊕ 1995 - 1997 ................................................. ⊕ 1993 - 1995 ................................................. ⊕ 1991 - 1993 ................................................. ⊕ 1989 - 1991 ................................................. ⊕ 1988 - 1989 ................................................. ⊕ 1985 - 1988 ................................................. ⊕ 1984 - 1985 ................................................. ⊕