Second seed Jelena Jankovic and sixth seed Venus Williams advanced to the quarterfinals of the Porsche Tennis Grand Prix in Stuttgart.
Williams served 12 aces on her way to a 6-4 6-2 victory over Ukraine’s qualifier Kateryna Bondarenko.
Jelena Jankovic, who will regain the world number one spot from Serena Williams, beat Kateryna’s older sister Alona Bondarenko 6-2 6-0 to win her opening match in Stuttgart.
Other quarterfinalists in Stuttgart:
Third seed Dinara Safina, one of four Russian quarterfinalists at the Porsche Tennis Grand Prix, beat Bulgaria’s Tsvetana Pironkova 6-1 7-6(6) to reach the last eight. She will next play Venus Williams.
Russian seventh seed Vera Zvonareva spoiled Marion Bartoli’s 24th birthday beating her 6-2 6-0, while another Russian Nadia Petrova defeated Swiss Patty Schnyder 6-4 6-1. Zvonareva’s next opponent will be Jelena Jankovic, and Petrova’s Li Na of China.
There is one more quarterfinal pair, fourth seed Elena Dementieva will play Belorussian Victoria Azarenka.