1. UNWC, Report of the World Commission on Environment and Development: Our Common Future. Oxford University Press, Oxford (1987). http://www.un-documents.net/our-common-future.pdf
2. Strategy, Riga Sustainable development strategy of Riga until 2030. Riga city development department, Rīga (2014). http://www.rdpad.lv/strategija/
3. UN ESCAP, Sustainable Urban Transportation Systems, United Nations Economic and Social Commission for Asia and the Pacific (UNESCAP) (2012). https://www.uncclearn.org/sites/default/files/inventory/unescap20_0.pdf
4. Jeon, C., Amekudzi, A.: Addressing sustainability in transportation systems: definitions. Indic. Metrics 11, 31–50 (2005)
5. Boschmanna, E.E., Kwana, M.P.: Toward socially sustainable urban transportation: progress and potentials. Int. J. Sustain. Transp. 2(3), 138–157 (2008)