Each HealthCare Providers applying to be Member of European Reference Networks should be endorsed nationnally. The HCPs / Centers of Excellence must indeed provide a letter of national endorsement together with its application and self-assessment forms. Some information on Each national processes are provided in the European Commission page on the Board of Member States here.
Updated information were published on April, 19th regarding national endorsement processes in: Germany, Spain, Netherlands, Malta, Norway, Finland, Belgium, and Poland.