1. Liu F Tong J Mao J Bohn R Messina J Badger L Leaf D NIST cloud computing reference architecture http://www.nist.gov/customcf/get_pdf.cfm?pub_id=909505
2. Google Google AppEngine 2008 http://code.google.com/appengine
3. Amazon Amazon elastic compute cloud 2002 http://aws.amazon.com/ec2
4. Rackspace, cloud hosting and storage services 2008 http://rackspace.com/cloud
5. Terremark enterprise cloud computing 2010 http://www.terremark.com/services/it-infrastructure/cloud-services/