Article 6 of Directive 79/267/EEC shall be replaced by the following:
'Article 6 The taking-up of the activities covered by this Directive shall be subject to prior official authorization. Such authorization shall be sought from the authorities of the home Member State by: (a) any undertaking which establishes its head office in the territory of that State; (b) any undertaking which, having received the authorization required in the first subparagraph, extends its business to an entire class or to other classes.'