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In what was a very one-sided encounter, Tomova could only win one game in an opening set that was completed with consummate ease by the American.
Williams, who is seeded 25th at SW19, conceded four games in the second set that was no more difficult but which allowed her to ease off.
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The seven-times champion took just 66 minutes to complete a comprehensive victory that continued her fine start to the tournament and took her winning streak at Wimbledon to 16 matches.
"It was better than my first round and I'm happy that I'm going in the right direction," Williams said.
She will next take on either France's Kristina Mladenovic or Tatjana Maria of Germany in the third round.
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Women's singles results
Phillip Island (2015)