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                 === Serena wins again at WTA Championships ===
 
 Istanbul, Turkey (Sports  Network)  - Two-time  titlist  Serena Williams
 improved to 2-0 in round-robin play at the season-ending WTA Championships in
 Istanbul.
 
 The third-seeded former top-ranked great Williams got past eighth-seeded
 former French Open champion Li Na, 7-6 (7-2), 6-3, indoors at Sinan  Erdem
 Arena. The powerful American smacked six aces in the 1-hour, 50-minute
 victory.
 
 The  2012 Wimbledon,  U.S. Open  and  Olympic champion  Williams captured  WTA
 Championships  titles  in 2001  and 2009  and is a  two-time runner-up at this
 prestigious event.
 
 This week's four-player Group A features world No. 1 Australian Open champion
 and U.S. Open  runner-up  Victoria Azarenka, Williams (2-0), Angelique Kerber
 (0-1) and Li (0-1), while Group B boasts 2004 champion and 2007 WTA
 Championships runner-up Maria Sharapova (1-0), Wimbledon runner-up Agnieszka
 Radwanska (1-0), French Open runner-up Sara Errani (0-1) and Sam Stosur, who
 replaced last year's Championships winner Petra Kvitova in the field after
 Kvitova (0-1) pulled out, citing a viral illness, after losing to Radwanska on
 Tuesday.
 
 The  top-two  players in  each group  will advance to  the semifinals and the
 winners will square off in the lucrative finale on Sunday.
 
 Azarenka needs only two wins this week to end the year at No. 1.
 
 The winner of this $4.9 million event could collect as much as $1.75 million.
 
 
 
 10/24 12:27:41 ET