In US Open tennis, Serena Williams take on Australian Sam Stosur in the women's singles final on Sunday .Williams beat Caroline Wozniacki 6-2, 6-4 in semi finals yesterday. 29-year-old US tennis star Serena Williams has won 13 grand slam singles titles, including three US Opens so far.Sam Stosur, sealed her place in the final with a 6-3, 2-6, 6-2 win over unseeded German Angelique Kerber. In Mens singles, Novak Djokovic and Rafal Nadal will meet in the event final tomorrow for the second year in a row.