1. Twitter. http://www.twitter.com/.
2. Harris county flood warning system. http://www.harriscountyfws.org/.
3. National seismological center, Nepal. http://www.seismonepal.gov.np/.
4. Caltrans performance measurement system (pems). http://pems.dot.ca.gov/.
5. On truth discovery in social sensing: A maximum likelihood estimation approach;Wang,2012