Who were Dürr's opponents in the final on year 1968?
CREATE TABLE "mixed_doubles_8_4_4" (
  "outcome" text,
  "year" real,
  "championship" text,
  "surface" text,
  "partner" text,
  "opponents_in_the_final" text,
  "score_in_the_final" text
);
SELECT "opponents_in_the_final" FROM "mixed_doubles_8_4_4" WHERE "year"=1968;