"National security United States." . . "Emergency management United States." . . . . "Terrorism United States Prevention." . . "United States. Department of Homeland Security." . . "Civil defense United States." . . . . . . . . . . . . . . . "Electronic books"@en . . . . . . . "Introduction to homeland security"@en . . . . . . . . . "Introduction to homeland security" . . . . . . "Homeland security"@en . .