A Península Ibérica em números 2017 [documento eletrónico] / Instituto Nacional de Estatística
E-Communications and digital single market [documento eletrónico] / European Commission
United Nations e-government survey 2018 [documento eletrónico] : gearing e-government to support transformation towards sustainable and resilient societies / United Nations
Measuring the information society report 2018 [documento eletrónico] / International Telecommunication Union