CREATE TABLE table_18557 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Result" CLOB, "Candidates" CLOB)

Which district has the incumbent Wilbur Mills and a re-elected result?
SELECT "District" FROM table_18557 WHERE "Result" = 'Re-elected' AND "Incumbent" = 'Wilbur Mills'
SELECT "District" FROM "table_18557" WHERE "Incumbent" = 'Wilbur Mills' AND "Result" = 'Re-elected'