42It should be borne in mind that Article 13 of the Authorisation Directive authorises Member States to set, in addition to charges designed to cover administration costs, a supplementary charge for the rights of use for radio frequencies with the purpose of ensuring optimal use of those resources (see, to that effect, Joined Cases C-327/03 and C-328/03 ISIS Multimedia Net and Firma O2 [2005] ECR I-8877, paragraph 23, and Telefónica Móviles España, paragraph 24).
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