1. European Parliament and Council 2014. Regulation (EU) No 910/2014 of the European Parliament and of the Council of 23 July 2014 on electronic identification and trust services for electronic transactions in the internal market and repealing Directive 1999/93/EC. En: https://eurlex.europa.eu/legal-content/EN/TXT/?uri=uriserv:OJ.L_.2014.257.01.0073.01.ENG European Parliament and Council 2014. Regulation (EU) No 910/2014 of the European Parliament and of the Council of 23 July 2014 on electronic identification and trust services for electronic transactions in the internal market and repealing Directive 1999/93/EC. En: https://eurlex.europa.eu/legal-content/EN/TXT/?uri=uriserv:OJ.L_.2014.257.01.0073.01.ENG
2. OpenPEPPOL 2019. PEPPOL eDelivery Network Portal. En: https://peppol.eu/ OpenPEPPOL 2019. PEPPOL eDelivery Network Portal. En: https://peppol.eu/
3. OpenPEPPOL 2019. PEPPOL eDelivery Network - An Overview. En: https://peppol.eu/what-is-peppol/peppol-transport-infrastructure/ OpenPEPPOL 2019. PEPPOL eDelivery Network - An Overview. En: https://peppol.eu/what-is-peppol/peppol-transport-infrastructure/
4. A General Quality Classification System for eIDs and e-Signatures
5. Generic Services for Cross Domain Use in e-Government