Five-time champion Venus Williams overcame a tough challenge from Jarmila Groth of Australia to reach the Wimbledon quarterfinals Monday, while No. 3 seed Caroline Wozniacki was knocked out in straight sets by unseeded Czech Petra Kvitova. Fourth-seeded Jelena Jankovic retired due to a back injury, while Kim Clijsters rallied to beat fellow Belgian Justine Henin in three sets. Venus Williams, the No. 2 seed, overcame a tough challenge from Groth, the lowest-ranked player left in the draw. She broke back twice to stay in the second set, then escaped in the tiebreaker to complete a 6-4, 7-6 (5) victory. http://sports.espn.go.com/sports/tennis/wimbledon10/news/story?id=5335405
