Helfer, L. (2013). Flexibility in International Agreements. In Interdisciplinary Perspectives on International Law and International Relations: The State of the Art (pp. 175–196).

Helfer, L. “Flexibility in International Agreements.” In Interdisciplinary Perspectives on International Law and International Relations: The State of the Art, 175–96, 2013.

Helfer L. Flexibility in International Agreements. In: Interdisciplinary Perspectives on International Law and International Relations: The State of the Art. 2013. p. 175–96.

Helfer, L. “Flexibility in International Agreements.” Interdisciplinary Perspectives on International Law and International Relations: The State of the Art, 2013, pp. 175–96.

Helfer L. Flexibility in International Agreements. Interdisciplinary Perspectives on International Law and International Relations: The State of the Art. 2013. p. 175–196.