Investigators who are trying to determine whether anyone in the Bush administration improperly disclosed the name of an undercover C.I.A. officer have asked some White House staff members to sign forms waiving their right to have private conversations with reporters, government officials said on Friday. The waiver forms were presented to the White House employees starting about a month ago, one official said, confirming a report broadcast on Friday evening by NBC News. However, it was not clear whether any of the staff members had actually signed the forms or disclosed the names of reporters with whom they had confidential conversations. Full Story