1. Population Facts (2021, September 14). United Nations. Population Division. World Urbanization Prospects 2018. United Nations, New York: United Nations Publications. Available online: https://population.un.org/wup/Publications/Files/WUP2018-PopFacts_2018-1.pdf.
2. United Nations (2021, September 15). Department of Economic and Social Affairs. Meeting Challenges for the Urban Future. Available online: https://sdgs.un.org/publications/meeting-challenges-urban-future-17398.
3. European Commission (2021, October 25). Mobility and Transport, Sustainable Urban Mobility Plans. Available online: https://transport.ec.europa.eu/transport-themes/clean-transport-urban-transport/urban-mobility/urban-mobility-actions/sustainable-urban-mobility-plans_en.
4. Commission of the European Communities (2021, October 25). Roadmap to a Single European Transport Area. Brussels, 28.3.2011 COM (2011) 144 Final. Available online: http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=COM:2011:0144:FIN:EN:PDF.
5. Vehicle Routing Problems for City Logistics;Absi;EURO J. Transp. Logist.,2017