That an import quota restricts supply and elevates domestic prices above world levels is a fundamental economic definition of the policy, requiring no formal citation.
The claim states a foundational definition and theoretical outcome of import quotas in international trade economics: by limiting the quantity of a good that may enter a country, quotas create scarcity and drive domestic prices above world market levels. This is a core textbook definition and common knowledge within economics, meaning no citation of specific empirical papers is required for proof.