OBS_VALUE: Note that construction firms must sign up to specfic registries in order to be allowed to bid for public contracts. Technical specifications shall not refer to a specific source, or a particular process which characterises the products or services provided by a specific economic operator with the effect of favouring certain undertakings or products (Article 54). The contracting authority sets out the criteria for selecting a tenderer, among which are economic and technical factors; one of the requirements may be registration at the Professional Registry (Article 75).