The Russians also raised questions about Tsarnaev's mother, Zubeidat Tsarnaev, according to several sources.

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More recently, according to several sources, Summers has become a forceful advocate for more aggressive intervention.

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According to several sources, Pearson Education Inc. have numerous multi-million dollar contracts with states throughout the country.

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Since then, the two men (and their families) have hardly communicated with each other, according to several sources familiar with their affairs.

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The Russians also raised questions about Tsarnaev's mother, Zubeidat Tsarnaev, when they approached the U.S. about concerns regarding Tamerlan Tsarnaev, according to several sources.

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But the White House firmly opposes the idea of letting pilots carry handguns in the cockpit, according to several sources who spoke to CNN on condition of anonymity.

CNN: Bush to propose aviation security measures Thursday

After Sehat left Berkeley in 1988, he boasted that he was the best analog engineer in the world, according to several sources. (Sehat says others might have said that but he never did.) "He was cocky at the time, " Pantas remembers.

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According to sources close to the company's landlords, contracts to operate several hundred homes could be removed from Southern Cross.

BBC: Southern Cross to lose hundreds of care homes