Memorandum from the Chairman, Scientific Estimates Committee, to the Chairman, Intelligence Advisory Committee, “Progress Report on Action Taken Pursuant to IAC Post-Mortem on NIE 11-5-57, Soviet Capabilities and Probable Programs in the Guided Missile Field (IAC-D-57/59, 21 March 1957, as approved in Item 3 a, IAC-M-281), SECRET, 19 September 1957