US Open 2011: Roger Federer struggles to accept Novak Djokovic defeat, US Open 2011

Roger Federer was left stung by Novak Djokovic's comeback in their five-set US Open semi-final

Roger Federer - Wikipedia

Federer, Djokovic advance to semis at Indian Wells - The San Diego Union-Tribune

2011 U.S. Open: Roddick Exits With an Empty Tank - The New York Times

Novak Djokovic stuns Roger Federer in US Open semi-final, Roger Federer

Djokovic–Federer rivalry - Wikipedia

Federer fails to impress, Tennis News

2012 French Open: Djokovic and Federer Survive to Set Up Semifinal Clash - The New York Times

2011 U.S. Open: Federer Is Set to Battle Djokovic in Semifinals - The New York Times

Roger Federer vs. Novak Djokovic: A Rivalry That Sizzles in the Paris Sun, News, Scores, Highlights, Stats, and Rumors

Novak Djokovic stuns Roger Federer in US Open semi-final, Roger Federer