D. Gefen, E. Karahanna, and D. W. Straub, Trust and TAM in online shopping: An integrated model, MIS Quarterly, vol.27, pp.51-90, 2003.

A. Beldad, M. De-jong, and M. Steehouder, How shall I trust the faceless and the intangible? A literature review on the antecedents of online trust, Computers in Human Behavior, vol.26, pp.857-869, 2010.

H. Krcmar, C. Akkaya, L. Müller, S. Dietrich, M. Boberach et al., eGovernment MONITOR 2017: Nutzung und Akzeptanz digitaler Verwaltungsangebote-Deutschland, Österreich und Schweiz im Vergleich Initiative D21, fortiss GmbH, 2017.

H. Krcmar, M. Dapp, R. Zepic, L. Müller, S. Dietrich et al., , 2016.

, European Commission. EU eGovernment Action Plan, 2016.

, European Commission: Tallinn Declaration on eGovernment, 2017.

D. Landkreistag, The New German Coalition Agreement, 2018.

M. A. Wimmer, E. Tambouris, R. Krimmer, J. R. Gil-garcia, and A. T. Chatfield, Once Only Principle: Benefits, Barriers and Next Steps, Proceedings of the 18th Annual International Conference on Digital Government Research, 2017.

R. Krimmer, T. Kalvet, M. Toots, A. Cepilovs, and E. Tambouris, Exploring and Demonstrating the Once-Only Principle: A European Perspective, 2017.

R. Buyle, L. De-vocht, M. Van-compernolle, D. De-paepe, R. Verborgh et al., Oslo: open standards for linked organizations, 2016.

L. Veiga, T. Janowski, and L. S. Barbosa, Digital government and administrative burden reduction, 2016.

T. Kalvet, M. Toots, and R. Krimmer, Contributing to a Digital Single Market for Europe: Barriers and Drivers of an EU-wide Once-Only Principle, Proceedings of the 19th Annual International Conference on Digital Government Research Delft, 2018.

A. Tikhomirova, Reinforcing Trust and Security in Digital Services and in the Handling of Personal Data. InterEU law east: journal for the international and european law, economics and market integrations, vol.3, pp.145-153, 2016.

R. Krimmer, T. Kalvet, M. Toots, and A. Cepilovs, The Once-Only Principle Project: Position Paper on Definition of OOP and Situation in, Europe, 2017.

, European Commission. A Digital Single Market Strategy, 2015.

J. Cave, M. Botterman, S. Cavallini, and M. Volpe, SMART 2015/0062: EU-wide digital Once-Only Principle for citizens and businesses, 2017.

R. Krimmer, , 2017.

. Scoop4c-webpage, European Commission: General Data Protection Regulation (GDPR) Portal, Austrian federal government commits to implementing once-only principle in new e-government plan, 2017.

, Nordic Institute for Interoperability Solutions (NIIS): Digital society solutions and cross

H. Krcmar, P. Wolf, L. Rau, V. Stavrakakis, and . Monitor, , 2014.

, Nutzung und Akzeptanz von elektronischen Bürgerdiensten im internationalen Vergleich, Initiative D21 e.V., Institute for Public Information Management (ipima, 2014.

H. Krcmar, P. Wolf, R. Zepic, L. Müller, V. Till-stavrakakis et al., Nutzung und Akzeptanz von elektronischen Bürgerdiensten im internationalen Vergleich, Initiative D21 e.V., Institute for Public Information Management (ipima), 2015.

. , European Commission: The Digital Economy and Society Index

. Capgemini and . Benchmark, , 2017.

B. Lotze, , 2017.

C. Akkaya, P. Wolf, and H. Krcmar, Factors influencing citizen adoption of e-Government services: A cross-cultural comparison, Proceedings of the 45 th Hawaii International Conference on System Science, 2012.

C. Akkaya, A Comprehensive Analysis on Citizen Adoption of E-Government Services: A Cross-Cultural Analysis, 2016.

T. Kalvet, M. Toots, and R. Krimmer, The Once-Only Principle Project: Drivers and Barriers for OOP, 2017.

M. Moon, Estonia freezes residen ID cards due to security flaw, 2017.