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Federer and Nadal progress to third round
Top seeds Roger Federer and Rafael Nadal continued their bids for Olympic gold with comfortable second-round victories in the men's singles.
Swiss top seed Federer had little difficulty in dispatching El Salvador's Rafael Arevalo 6-2 6-4, while Nadal brushed aside Lleyton Hewitt 6-1 6-2.
Serbia's third seed Novak Djokovic beat Germany's Rainer Schuettler 6-4 6-2.
Meanwhile, sisters Serena and Venus Williams recorded second-round victories in the women's singles.
Fourth seed Serena crushed Australia's Samantha Stosur 6-3 6-0, while seventh seed Venus was too strong for Iveta Benesova, winning 6-1 6-4.
Serena missed the 2004 Games in Athens because of injury
"It was clean," said Serena. "My way of improving on it is to keep it up."
Serena was in total control against Stosur, taking only 44 minutes to wrap up victory.
From 2-2 in the opening set, she won 40 of the final 49 points, losing only five points in the second set.
Venus struggled with her second serve in her match, hitting six double-faults, but she never faced a break point and lost only two of 24 points on her first serve.
Serena and Venus, who also play together in the doubles, could meet in the singles final.
Meanwhile, back in the men's draw, Spain's Nadal, who will take over from Federer as world number one next week, was relentless against Hewitt.
The Australian was noticeably tired after a gruelling doubles match which had stretched into the early hours of Tuesday morning.
Nadal said: "I played very well. It was one of the best matches I have played."
The Wimbledon champion will next play Russian Igor Andreev in the third round, while Federer will face 17th seed Tomas Berdych of the Czech Republic.
There was bad news for the men's defending Olympic champion Nicolas Massu of Chile as he lost 7-6 6-1 to the seventh seed David Nalbandian.
And in the surprise result of the round, Russian fourth seed Nikolay Davydenko lost 7-5 6-3 to Paul-Henri Mathieu.
Mathieu will be joined in the next round by French compatriots Gilles Simon and Gael Monfils after their respective wins over Guillermo Canas of Argentina and Romanian Victor Hanescu.
In other matches, the women's top seed Jelena Jankovic eased past Ukraine's Alona Bondarenko 7-5 6-1.
The 23-year-old, who was wearing a strapping on her right calf, said: "I took some painkillers to be able to play, otherwise it's quite sore.
"It was already much better than Monday when I was in a lot of pain. But I hope to be improving further for Wednesday."
Tenth seed Daniela Hantuchova and eighth seed Agnieszka Radwanska both crashed out.
Hantuchova of Slovakia lost 6-1 6-3 to Denmark's Caroline Wozniacki, while Radwanska of Poland was defeated 6-3 7-6 (8-6) by Italy's Francesca Schiavone.