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Photo by: Emilio Morenatti

An Egyptian army lieutenant colonel stands on top of a tank as demonstrators arrive in Tahrir, or Liberation, Square in Cairo on Tuesday, Feb. 1, 2011. More than a quarter-million people flooded into the heart of Cairo, filling the city's main square in by far the largest demonstration in a week of unceasing demands for President Hosni Mubarak to leave after nearly 30 years in power. (AP Photo/Emilio Morenatti)

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