@Book{Kennedy1991,
  author = {Kennedy, Paul},
  title  = {Aufstieg und Fall der großen Mächte. Ökonomischer Wandel und militärischer Konflikt von 1500 bis 2000},

  year   = {1991},
  number = {},
  url    = {},

  const  = {\ text}
}
@Book{Czempiel1989,
  author = {Czempiel, Ernst-Otto and Rosenau, James N.},
  title  = {Global Changes and Theoretical Challanges. Approaches to World Politics for the 1990s},

  year   = {1989},
  number = {},
  url    = {},

  const  = {\ text}
}