“ For the purposes of this section registered mail in the custody of a transporting agency of the United States Post Office is considered within United States Government control unless the transporting agent is foreign controlled or operated. Secret information and material may, however, be transmitted between United States Government or Canadian Government installations, or both, in the forty-eight contiguous States, the District of Columbia, Alaska, and Canada by United States and Canadian registered mail with registered mail receipt. ”

“ Heads of departments or agencies originating classified information or material shall designate persons to be responsible for continuing review of such classified information or material on a document-by-document, category, project, program, or other systematic basis, for the purpose of declassifying or downgrading whenever national defense considerations permit, and for receiving requests for such review from all sources. ”

“ By virtue of the authority vested in me by the Constitution and statutes of the United States, and deeming such action necessary in the best interest of the national security, it is ordered that Executive Order No. ”