Roger Federer is taking tips from his six-year-old twin daughters in his quest to break his grand slam title drought. Federer enters his Australian Open quarter-final against Tomas Berdych on Tuesday unlikely to need too much help to take care of the sixth-seeded Czech for a 16th time.  
But a looming semi-final with Novak Djokovic presents a real challenge for the third seed who has fallen to his Serbian nemesis in three grand slam finals in the past 18 months. Federer's daughters had their heads buried in books during his second-round win over Alexander Dolgopolov, but they do offer dad advice occasionally - Myla Rose and Charlene Riva urging him to shoot for the lines. "The one thing in tennis they tell me is I should play on the lines. They think that's a good thing," Federer said. "I said I would try that. The other gem was, '  Maybe you should look that way and play the other way.' I said, 'OK, I'll try that, too. It's not as easy as you think it is, but I'll try.' " They're good coaches, yeah." Federer says he is treating Berdych with respect as the underdog bids for a place in the final four in Melbourne for the third straight year.