CREATE TABLE table_55919 ("Season" CLOB, "Club" CLOB, "National League" CLOB, "National Cup" CLOB, "European Cup" CLOB)

Which European Cup is in the 1990-91 season?
SELECT "European Cup" FROM table_55919 WHERE "Season" = '1990-91'
SELECT "European Cup" FROM "table_55919" WHERE "Season" = '1990-91'