CREATE TABLE table_4454 ("Shipyard" TEXT, "Laid down" TEXT, "Launched" TEXT, "Commissioned" TEXT, "Fleet" TEXT, "Status" TEXT)

Which shipyard has a fleet that was laid down on April 21, 1962?
SELECT "Shipyard" FROM table_4454 WHERE "Laid down" = 'april 21, 1962'
SELECT "Shipyard" FROM "table_4454" WHERE "Laid down" = 'april 21, 1962'