CREATE TABLE table_20320 ("Series #" FLOAT, "Season #" FLOAT, "Title" TEXT, "Directed by:" TEXT, "Written by:" TEXT, "Original air date" TEXT)

Which titles were directed by George Blair and written by Jackson Gillis?
SELECT "Title" FROM table_20320 WHERE "Directed by:" = 'George Blair' AND "Written by:" = 'Jackson Gillis'
SELECT "Title" FROM "table_20320" WHERE "Directed by:" = 'George Blair' AND "Written by:" = 'Jackson Gillis'