1. P. Mell, T. Grance, The NIST definition of cloud computing, Tech. Rep. (accessed February 2013).
2. How many data centers?, http://www.datacenterknowledge.com/archives/2011/12/14/how-many-data-centers-emerson-says-500000/ (accessed March 2013).
3. Google uses over one million servers, http://www.extremetech.com/extreme/131962-google-compute-engine-for-2-millionday-your-company-can-run-the-third-fastest-supercomputer-in-the-world/ (accessed September 2013).
4. Power, pollution and the internet, http://www.nytimes.com/2012/09/23/technology/data-centers-waste-vast-amounts-of-energy-belying-industry-image.html (accessed April 2013).
5. 5 data center trends for 2013, http://www.informationweek.com/hardware/data-centers/5-data-center-trends-for-2013/240145349 (accessed March 2013).