Continental defense warning systems of the North America. Continental Air Defense Command areas of responsibility
U.S. Department of Defense
<a rel="nofollow" class="external text" href="https://babel.hathitrust.org/cgi/pt?id=osu.32435062847025;view=1up;seq=14">Annual Report of the Secretary of Defense. July 1, 1958 to June 30, 1959</a>, Page 6, Figure 2. Continental Defense Warning Systems