In the indictment, Libby is being charge mainly with claiming Russert mentioned Plame to him first. Then, according to Libby, he mentioned it to Cooper and to Miller, but said he personally wasn't sure of her status. White House documents apparently show that to be false. Also, the specificity of the rebuttal of the Russert claim hints that either Russert recorded the conversation which would probably be inadmissable, or that someone else was listening in and confirmed the testimony. That would seem to be the strongest part of the indictment just from simple reading of it. The material part of the perjury would seem to stem from Libby claiming that he didn't know Plame's status for sure when apparently multiple sources demonstrate he was well aware of it since he had been investigating Wilson and Plame as part of his duties as the VP's Chief of Staff since people were making claims against Cheney.