1. Kalvet, T., Toots, M., van Veenstra, A.F., Krimmer, R.: Cross-border e-government services in Europe: expected benefits, barriers and drivers of the once-only principle. In: ICEGOV’18 Proceedings of the 11th International Conference on Theory and Practice of Electronic Governance, pp. 69–72 (2018)
2. European Union: Regulation (EU) 2018/1724 of the European Parliament and of the Council of 2 October 2018 establishing a single digital gateway to provide access to information, to procedures and to assistance and problem-solving services and amending Regulation (EU) No 1024/2012 (2018)
3. Bielowski, A., et al.: D2.7 Interoperability architecture for cross-border procedures and evidence exchange in light of the single digital gateway regulation. DE4A deliverable D2.7 (2022). https://www.de4a.eu/project-deliverables
4. Schmidt, C., Krimmer, R.: How to implement the European digital single market: identifying the catalyst for digital transformation. J. Eur. Integr. 44(1), 59–80 (2022)
5. Klobučar, T., et al.: D4.4 studying abroad – final running phase. DE4A deliverable D4.4 (2023). https://www.de4a.eu/project-deliverables