++++ Tax provisions - Harmonization of legislation - Turnover taxes - Common system of value-added tax - Exemptions provided for by the Sixth Directive - Strict interpretation - Exemption of services supplied by independent groups of persons exercising an activity which is exempt or for which they are not taxable, for the purpose of rendering services to their members - Organization and performance by a foundation of services which are related to the activities of another foundation which qualifies for the exemption - Not permissible ( Sixth Council Directive ( 77/388/EEC ), Art . 13(A)(1)(f ) )