Table: tennis_match_results_3
Columns: outcome
year
championship
surface
partner
opponents_in_the_final
score_in_the_final

Question: Who were Dürr's opponents in the final on year 1968?
SQL: SELECT "opponents_in_the_final" FROM tennis_match_results_3 WHERE "year" = 1968

Question: What was the court surface on year 1971?
SQL: SELECT "surface" FROM tennis_match_results_3 WHERE "year" = 1971