ITU‐T's Technical Reports and Specifications 57 For each definition, a set of key words was extracted and tabulated. These keywords were then grouped under some common themes. Some words such as \"smart\" and \"city\" are implicit and were mentioned in almost every description, so they are not captured explicitly as a separate keyword. 4.3 Approach A systematic approach was followed throughout the study including: Top down approach – indicators, indices, and rankings. Bottom up approach – definitions, attributes, and descriptors. As part of the research, multiple words and combinations thereof were used during the search from primary sources. Primary search words included (but not limited to): smart, sustainable, environment, city/cites, definition, attributes, index, indicator, characteristics, ICT, intelligent, urban, methodology, solution, example, success, and ranking. A detailed analysis of different key words and attributes and perspectives from these diverse sources was performed. Such an approach has provided a truly diverse set of definitions and supplied a sense of \"completeness\" or comprehensiveness to the study. Based on the definitions, a series of keywords was identified and documented as illustrated in the sample below in Table 1: Table 1 – Sample table depicting the definitions, keywords and the respective sources for each Source Definitions Keywords Giffinger, Rudolf, et al.. \"Smart Cities Ranking of European Medium‐sized Cities.\" Centre of Regional Science, Vienna UT, Oct. 2007. Page 10. Web. Last Accessed 8 Feb. 2014. http://www.smart‐cities.eu/download/smart_ cities_ final_ report.pdf \"A city well performing in a forward‐looking way in [economy, people, governance, mobility, environment, and living] built on the smart combination of endowments and activities of self‐decisive, independent and aware citizens.\" Economy, people, governance, mobility, environment, quality of living, forward looking, aware citizens, self‐decisive citizens, independent citizens. Cohen, Boyd. \"The Top 10 Smart Cities On The Planet.\" Fast Company, 11 Jan. 2011. Web. Last accessed 12 Feb. 2014. http://www.fastcoexist.com/16791 27/the‐top‐10‐smart‐cities‐on‐the‐planet . Smart sustainable cities use information and communication technologies (ICT) to be more intelligent and efficient in the use of resources, resulting in cost and energy savings, improved service delivery and quality of life, and reduced environmental footprint – all supporting innovation and the low‐carbon economy. ICT, cost efficiency, energy efficiency, energy savings, quality of life, environment, improved service delivery, innovation, low carbon economy.