Cross-border e-government services in Europe: expected benefits, barriers and drivers of the once-only principleKalvet, Tarmo; Toots, Maarja; Veenstra, Anne Fleur van; Krimmer, Robert JohannesICEGOV2018 : proceedings of the 11th International Conference on Theory and Practice of Electronic Governance : 4 - 6 April 2018, Galway, Ireland2018 / p. 59-68 https://doi.org/10.1145/3209415.3209458 Conference proceedings at Scopus Article at Scopus Article at WOS