1. Robert Müller-Török , Alexander Prosser . 2019. SAP® ECC in the Public Sector . Facultas , Vienna . Robert Müller-Török, Alexander Prosser. 2019. SAP® ECC in the Public Sector. Facultas, Vienna.
2. IT Planungsrat. 2021. Föderale Architekturrichtlinien. Download from https://www.fitko.de/fileadmin/fitko/foederale-koordination/gremienarbeit/Foederales_IT-Architekturboard/Foederale_IT-Architekturrichtlinien_V1.0.pdf IT Planungsrat. 2021. Föderale Architekturrichtlinien. Download from https://www.fitko.de/fileadmin/fitko/foederale-koordination/gremienarbeit/Foederales_IT-Architekturboard/Foederale_IT-Architekturrichtlinien_V1.0.pdf
3. Bodo Leibinger Reinhard Müller Bernd Züll. 2021. Öffentliche Finanzwirtschaft. R.v.Decker Heidelberg. Bodo Leibinger Reinhard Müller Bernd Züll. 2021. Öffentliche Finanzwirtschaft. R.v.Decker Heidelberg.
4. European Parliament. 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. Download from https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32014R0910 European Parliament. 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. Download from https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32014R0910
5. Santosh Chokhani , Warwick Ford Randy V. Sabett Charles R. Merrill . 2003 . RFC 3647, Internet X.509 Public Key Infrastructure Certificate Policy and Certification Practices Framework. IETF Network Working Group . https://datatracker.ietf.org/doc/html/rfc3647 Santosh Chokhani, Warwick Ford Randy V. Sabett Charles R. Merrill. 2003. RFC 3647, Internet X.509 Public Key Infrastructure Certificate Policy and Certification Practices Framework. IETF Network Working Group. https://datatracker.ietf.org/doc/html/rfc3647