Table schema:
CREATE TABLE table_28211674_3 (mixed_veteran VARCHAR, womens_singles VARCHAR, mens_singles VARCHAR)

Question: When Naomi Owen won the Womens Singles and Ricardo Walther won the Mens Singles, who won the mixed veteran?
SQL: SELECT mixed_veteran FROM table_28211674_3 WHERE womens_singles = "Naomi Owen" AND mens_singles = "Ricardo Walther"