Ces États prennent de telles mesures individuellement ou conjointement et, le cas échéant, de concert avec des organisations internationales ou par leur entremise.

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Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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They shall take such action individually or jointly and, where appropriate, together with or through international organizations.