Doha, Qatar ? Serena Williams and Ana Ivanovic withdrew from the WTA’s season-ending event on Friday, when top-ranked Jelena Jankovic advanced despite losing, 2-6, 6-3, 6-4, to Vera Zvonareva.

Zvonareva and Jankovic both advanced to the semifinals of the Sony Ericsson Championships because of winning records in the round-robin stage of the tournament. Zvonareva plays Elena Dementieva, and Jankovic faces Venus Williams today.