Frei, D., & Ruloff, D. (1989). Handbook of foreign policy analysis: Methods for practical application in foreign policy planning, strategic planning, and business risk assessment. Dordrecht, The Netherlands Boston Norwell, MA, U.S.A: M. Nijhoff: Sold and distributed in the U.S.A. and Canada by Kluwer Academic Publishers.

Frei, Daniel, and Dieter Ruloff. Handbook of Foreign Policy Analysis: Methods for Practical Application in Foreign Policy Planning, Strategic Planning, and Business Risk Assessment. Dordrecht, The Netherlands Boston Norwell, MA, U.S.A: M. Nijhoff: Sold and distributed in the U.S.A. and Canada by Kluwer Academic Publishers, 1989.

Frei, Daniel, and Dieter Ruloff. Handbook of Foreign Policy Analysis: Methods for Practical Application in Foreign Policy Planning, Strategic Planning, and Business Risk Assessment. Dordrecht, The Netherlands Boston Norwell, MA, U.S.A: M. Nijhoff: Sold and distributed in the U.S.A. and Canada by Kluwer Academic Publishers, 1989.