CREATE TABLE table_28211674_3 (mixed_veteran VARCHAR(255), womens_singles VARCHAR(255), mens_singles VARCHAR(255))
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"