Beyond horizons [elektronický zdroj] : a half century of Air Force space leadership / David N. Spires ; senior editor, George W. Bradley III ; associate editors, Rick W. Sturdevant, Richard S. Eckert..    [Peterson Air Force Base, Colo.] : Air Force Space Command in association with Air University Press ; Washington, DC : For sale by the U.S. G.P.O., 1998. . 1 online resource (xxiii, 383 p.) ill. . ISBN 9781429492362 (electronic bk.). ISBN 1429492368 (electronic bk.)