Englisch version
- (International Telecommunication Union (ITU), 2019)
- (OECD, 2001)
- (National Telecommunications and Information Administration, NTIA, 1999)
- (Cerno & Pérez-Amaral, 2006)
- (Hacker & Mason, 2003)
- (Cava-Ferreruela & Alabau-Muñoz, 2006)
- (Srinuan & Bohlin, 2011)
- (Demoussis & Giannakopoulos, 2006)
- (Barzilai-Nahon, 2006)
- (Vehovar et al., 2006)
- (van Dijk, 2006)
- (Hilbert, 2016)
- (Ono & Zavodny, 2007)
- (Hilbert, 2011)
- (Zoroja, 2011)
- (Bach et al., 2013)
- (Salemink et al., 2017)
- (Ruiz-Rodríguez et al., 2018)
- (Nishijima et al., 2017)
- (Szeles, 2018)
- (Pérez-Amaral et al., 2020)
- (INE. Instituto Nacional de Estadística. National Statistics Institute. Spanish Statistical Office., 2020)
- (European Commission, 2019b)
- (European Commission, 2019a)
- (Nishijima et al., 2017)
- (Salemink et al., 2017)
- (Hilbert, 2016)
- (Szeles, 2018)
- (Zoroja, 2011)
- (Ruiz-Rodríguez et al., 2018)
- (Ono & Zavodny, 2007)
- (Garín-Muñoz et al., 2019)
- (Pérez-Amaral et al., 2020)
- (Cava-Ferreruela & Alabau-Muñoz, 2006)
- (van Dijk, 2006)
