Table 2.

Smart cities themes and references within the literature

Theme	References
Privacy and security of mobile devices and services	Abi Sen et al. (2018); Li et al. (2019)
Smart city infrastructure	Abosaq (2019); Ainane et al. (2018); Alandjani (2018); Antoine Picon (2019); Awad et al. (2019); Baryshev et al. (2016); Bernardes et al. (2018); Chatterjee et al. (2017); de Amorim et al. (2019); de Fuentes et al. (2017); Efthymiopoulos (2015); Elmaghraby and Losavio (2014); Evans (2018); Ferraz and Ferraz (2014a); Hiller and Blanke (2017); Jameel et al. (2019); Khan et al. (2014); Li et al. (2015); Liao et al. (2017); Liu et al. (2017); Pérez-Martínez et al. (2013); Rohokale and Prasad (2017); Vitunskaite et al. (2019); Waedt et al. (2016); Wang et al. (2012); Zhu and Zuo (2015)
Smart power systems	Ainane et al. (2018); Alamaniotis et al. (2017); Karasevich et al. (2016); Sanduleac et al. (2016)
Smart healthcare	Alromaihi et al. (2018); Huang et al. (2017); De Fuentes et al. (2018)
Frameworks, algorithms and protocols to improve security and privacy	Al-Dhubhani et al. (2018); Antonopoulos et al. (2017); Avgerou et al. (2016); Beltran et al. (2017); Burange and Misalkar (2015); Cagliero et al. (2015); de Fuentes et al. (2017); Ferdowsi et al. (2017); Gheisariy et al. (2019); González García et al. (2017); Gope et al. (2018); Guo et al. (2017); Han et al. (2019); Huerta and Salazar (2019) ; Khedr et al. (2019); Krichen and Alroobaea (2019); Krichen et al. (2018); Lai et al. (2017); Lepinski et al. (2016); Luo et al. (2017); Mazhelis et al. (2016); Patsakis et al. (2015); Peters et al. (2019); Roldan et al. (2019); Sen et al. (2013); Shen et al. (2017); Song et al. (2017); Stromire and Potoczny-Jones (2018); Sucasas et al. (2018); Sucasas et al. (2016); Berg et al. (2019); Wibowo (2018); Witti and Konstantas (2018); Xiao et al. (2017); Xie and Hwang (2019); Yilei and Leyou (2019); Zang et al. (2017)
Operational threats for smart cities	Aldairi and Tawalbeh (2017); Baig et al. (2017); Dewi Rosadi et al. (2018); Dhungana et al. (2015); Ferraz and Ferraz (2014b); Galdon-Clavell (2013); Grieman (2019); Habibzadeh et al. (2018); Kitchin and Dodge (2019); Pérez-Martínez et al. (2013); Techatassanasoontorn and Suo (2010); Vattapparamban et al. (2016); Velasquez et al. (2018); Yang and Xu (2018)
Use and adoption of smart services by citizens (success of smart services)	Babdullah et al. (2017); Belanche-Gracia et al. (2015); Chatterjee et al. (2018); Cilliers and Flowerday (2014); Cilliers and Flowerday (2015); Slade et al. (2013); Slade et al. (2014); Van Heek et al. (2016); van Zoonen (2016)
Use of blockchain systems within smart cities	Mora et al. (2019); Noh and Kwon (2019); Ramos and Silva (2019)
Social media and smart cities	Moustaka et al. (2019)