CREATE TABLE table_37992 ("Date" CLOB, "Opponent" CLOB, "Site" CLOB, "Result" CLOB, "Attendance" CLOB)

What is the Date at memorial stadium minneapolis, mn, and an Opponent of northwestern?
SELECT "Date" FROM table_37992 WHERE "Site" = 'memorial stadium • minneapolis, mn' AND "Opponent" = 'northwestern'
SELECT "Date" FROM "table_37992" WHERE "Opponent" = 'northwestern' AND "Site" = 'memorial stadium • minneapolis, mn'