CBS News says it cannot prove the authenticity of documents purporting to be memos from a Texas military official. The documents were used in a 60 Minutes 2 report questioning President Bush's service in the Texas Air National Guard. In a statement Monday, CBS News president Andrew Heyward said, "after doing extensive additional reporting the network cannot prove the documents are authentic, which is the only acceptable journalistic standard to using them in the report." NPR's Neda Ulaby reports.

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