A missing memorandum documenting a conversation between former President Lyndon B. Johnson and ex-CIA Director John McCone days after President Kennedy's assassination could contain crucial information that was never submitted to the National Archives, according to an author.

James H. Johnston, author of "Murder, Inc., the CIA under John F. Kennedy," told NewsNation that the memorandum was written following a private hourlong conversation between Johnson and McCone at the author's residence six days after the former president's death.

His comments come following the release of the remaining classified files on the assassination of Kennedy were released Tuesday on the National Archives website.

"John McCone always wrote a memorandum for the record of any conversation he had with the president," Johnston said Wednesday on NewsNation's........

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