Mediamatters gets to the heart of it:
Summary: In his latest column, Bob Novak purported to discuss his role in the federal investigation into the disclosure of former CIA operative Valerie Plame's identity, but instead of providing the answer to perhaps the most enduring mystery in this case -- the identity of his original source -- he repeated a number of false and contradictory statements regarding the investigation and the manner in which he learned of Plame's identity.
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In his July 12 nationally syndicated column, Fox News political analyst Robert D. Novak claimed to make good on his promise to discuss his role in the federal investigation into the disclosure of former CIA operative Valerie Plame's identity. But he did not provide the answer to perhaps the most enduring mystery in this case -- the identity of his original source -- and repeated false and contradictory statements regarding the investigation and the manner in which he learned of Plame's identity. The only discernible new disclosure in Novak's column was that he in fact testified before the grand jury and revealed his sources there.
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lots of supporting evidence at:
http://mediamatters.org/items/200607120006