1. What is OpenStack.
http://opensource.com/resources/what-is-openstack
2. Gormley, C., Tong, Z.: Elasticsearch the Definitive Guide. Shroff (2015)
3. The Elastic Platform.
https://www.elastic.co/products
4. Turnbull, J.: The Logstash Book—Log Management Made Easy, v1.5.1 (2015)
5. How To Install Elasticsearch: Logstash, and Kibana 4 on Ubuntu 14.04.
https://www.digitalocean.com/community/tutorials/how-to-install-elasticsearch-logstash-and-kibana-4-on-ubuntu-14-04