Contributing to a digital single market for Europe: barriers and drivers of an EU-wide once-only principleKalvet, Tarmo; Toots, Maarja; Krimmer, Robert Johannesdg.o 18 : Proceedings of the 19th Annual International Conference on Digital Government Research : Governance in the Data Age : Delft, Netherlands, May 30-June 01, 20182018 / Article No. 45, 8 p https://doi.org/10.1145/3209281.3209344 Conference proceedings at Scopus Article at Scopus Article at WOS

Exploring and demonstrating the once-only principle : a European perspectiveKrimmer, Robert Johannes; Kalvet, Tarmo; Toots, Maarja; Cepilovs, Aleksandrs; Tambouris, Efthimiosdg.o 2017 : the proceedings of the 18th Annual International Conference on Digital Government Research : Innovations and Transformations in Government : June 7-9, 2017, Staten Island, NY, USA2017 / p. 546-551 : ill https://doi.org/10.1145/3085228.3085235