1. http://an.kaist.ac.kr/traces/WWW2010.html. http://an.kaist.ac.kr/traces/WWW2010.html.
2. http://lamda.nju.edu.cn/zhangt/dm2012/Project4.html. http://lamda.nju.edu.cn/zhangt/dm2012/Project4.html.
3. arXiv. http://www.arxiv.org. arXiv. http://www.arxiv.org.
4. Empath: Sentiment Topic and Demographic Analysis. https://www.parc.com/services/focus-area/bigdata/. Empath: Sentiment Topic and Demographic Analysis. https://www.parc.com/services/focus-area/bigdata/.
5. Natural Language Sentiment Analysis API. http://text-processing.com/demo/sentiment/. Natural Language Sentiment Analysis API. http://text-processing.com/demo/sentiment/.