4. Where public sector bodies charge fees, they shall take measures to provide incentives for the re-use of the categories of data referred to in Article 3(1) for non-commercial purposes, such as scientific research purposes, and by SMEs and start-ups in accordance with State aid rules. In that regard, public sector bodies may also make the data available at a discounted fee or free of charge, in particular to SMEs and start-ups, civil society and educational establishments. To that end, public sector bodies may establish a list of categories of re-users to which data for re-use is made available at a discounted fee or free of charge. That list, together with the criteria used to establish it, shall be made public.