CREATE TABLE table_2961 ("Name" CLOB, "Aperture m" CLOB, "Aper. in" CLOB, "Mirror/type" CLOB, "Nationality/Sponsors" CLOB, "Site" CLOB, "Built/Used" CLOB)

Which aperture were built or used between 1987-2001?
SELECT "Aper. in" FROM table_2961 WHERE "Built/Used" = '1987-2001'
SELECT "Aper. in" FROM "table_2961" WHERE "Built/Used" = '1987-2001'