Samantha Stosur ousted in semis
The 134th-ranked Chang broke Stosur twice in the opening set. She eliminated three seeded players on the way to her first career WTA Tour final.
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Watson broke Doi four times in the second set to make up for losing her own serve three times.
The 20-year-old Watson also will be appearing in her first career WTA final -- just three weeks after Laura Robson became the first British woman in 22 years to reach a title match.
Copyright 2012 by The Associated Press