A featured Government Document is Toward a Theory of Spacepower: Selected Essays, from the Institute for National Strategic Studies. It's edited by Charles D. Lutes et al.
It's a fascinating volume on an intriguing and partially-frightening concept. The intro says the essays in the book define spacepower as "the ability to use space to influence others, events, or the environment to achieve one's purposes or goals." Further, it states that spacepower theorists draw on sea, land, and airpower as analogies.
Essays discuss International Discussions Theory as applied to spacepower; Stategic Theory, Military Theory, the role of the President of the United States in spacepower, "real constraints" on spacepower, and many other topics.