Read the “SAGE” article from the History of Computers for a longer, narrative history and description of the computer system.
This film on SAGE from the 1960s covers the necessity of the system, its components, the institutions that collaborated on SAGE, the teams that interacted to control SAGE, and a ‘simulation’ of how an attack on the US would be prevented by SAGE.
IEEE: “History and Design of the SAGE Computer – The AN/FSQ-7, Morton M. Astrahan, John F. Jacobs. This article discusses the design of the SAGE computer and the software systems that went into it. Beginning with pre-SAGE systems and the need for SAGE, it goes on to discuss the plans for SAGE and the innovations introduced by the computer.
Campbell-Kelly and Aspray, Computer: A History of the Information Machine, 148-152