A few suggestions...

Heil, Alan L., Jr. Voice of America: A History. Columbia University
Press, 2003.

Nelson, Michael. War of the Black Heavens: The Battles of Western
Broadcasting in the Cold War. Syracuse University Press, 1997.

Puddington, Arch. Broadcasting Freedom: The Cold War Triumph of Radio
Free Europe and Radio Liberty. University of Kentucky Press, 2000.

Urban, George R. Radio Free Europe and the Pursuit of Democracy: My
War Within the Cold War. Yale University Press, 1997.

You can often find nice discounts by searching through the
used/remainder books on Amazon. Happy readin', folks.

Junius