Greece depends heavily on tourism, but the economic crisis is driving away visitors like these ones photographing the Acropolis in Athens from the top of a tour bus last October. Louisa Gouliamaki/AFP/Getty Images hide caption

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Despite the multiple layers of security at airports, terrorists still often target planes. But terrorism analysts say they are also concerned about soft targets. Here, a Transportation Security Administration agent looks at an identity card at the Portland International Airport earlier this month. Rick Bowmer/AP hide caption

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Oil and gas production in the U.S. is rising, and the U.S. is expected to be less dependent on foreign energy in the coming years. This oil drilling rig, shown in October 2011, is outside Watford City, N.D., a state that has seen a boom in energy production. Matthew Staver/Landov hide caption

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The current case of a prominent Chinese activist seeking U.S. protection has echoes of a similar episode in 1989. Then, physicist Fang Lizhi took refuge at the U.S. Embassy in Beijing. He spent a year there before the U.S. and China reached a deal allowing him to move to the U.S. He died this month in Arizona, at age 76. John B. Carnett/Popular Science via Getty Images hide caption

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European leaders keep getting driven from office by voters upset with the continent's ongoing economic problems. French President Nicolas Sarkozy, shown here at a campaign event on Thursday, is trailing in opinion polls in advance of a May 6 runoff election. Lionel Bonaventure/AFP/Getty Images hide caption

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Sudanese President Omar al-Bashir visits the southern town of El-Obeid on April 19 amid rising tensions with South Sudan. The countries have been skirmishing, and there are fears of a full-scale war. Bashir says South Sudan's leaders only understand "the language of the gun." Ebrahim Hamid/AFP/Getty Images hide caption

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The Formula One Grand Prix Race set for Sunday in Bahrain has drawn attention to the island nation that was rocked by protests last year. Demonstrators are being kept away from the racing circuit. Driver Nico Rosberg of the Mercedes team is shown here during a practice session Friday. Karim Jaafar/AFP/Getty Images hide caption

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Argentine President Cristina Fernandez holds a petroleum sample as she announces plans for her government to nationalize a giant oil company that is largely owned by a private Spanish company, Repsol. Behind her is an image of the country's former first lady, Eva Peron. Daniel Garcia/AFP/Getty Images hide caption

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The U.S. now imports far more oil from Canada than from any other country. Persian Gulf imports now account for less than 15 percent of the oil consumed in the U.S. This photo shows the Syncrude oil sands extraction facility near Fort McMurray, Alberta, Canada, in 2009. Mark Ralston/AFP/Getty Images hide caption

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Tuareg rebels eat a meal last month near the Malian city of Timbuktu, which they recently captured. The rebels have taken control of northern Mali, raising concerns about stability in the broader region. Ferhat Bouda/DPA/Landov hide caption

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A patient is treated at the Nord Hospital in Marseille, France, in February. European countries have also been engaged in intense debates on the future of their health care systems, where universal coverage is the norm. Anne-Chrisine Poujoulat/AFP/Getty Images hide caption

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The leader of the junta that seized power in Mali, Army Capt. Amadou Sanogo, announces a curfew in the capital, Bamako, on Thursday, in this photo taken from television.The coup ousted an elected president who was due to step down after a new election next month in the West African nation. Issouf Sanogo/AFP/Getty Images hide caption

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