What does ^ mean in the reference?

What does ^ mean in the reference?

Context:

1.^ Gilbert Cruz (2009-02-25). "Commerce Secretary: Gary Locke". Time. http://www.time.com/time/politics/article/0,8599,1881587,00.html. Retrieved 2009-03-25.
2.^ a b "Remarks by President Obama and Commerce Secretary Nominee Gary Locke". Whitehouse.gov. February 25, 2009. http://www.whitehouse.gov/the_press_office/Remarks-by-President-Obama-and-Commerce-Secretary-Nominee-Gary-Locke/. Retrieved 2009-07-12.
3.^ Frank Chesley (2006-06-29). "Locke, Gary Faye (b. 1950)". HistoryLink. http://www.historylink.org/index.cfm?displaypage=output.cfm&file_id=7830. Retrieved 2009-03-25.
4.^ "Biography of Governor Gary Locke". Who's Who of Asian Americans. http://www.asianamerican.net/bios/Locke-Gary.html. Retrieved November 9, 2008.
5.^ http://www.chinareviewnews.com/doc/1008/9/8/9/100898991.html?coluid=9&kindid=3150&docid=100898991&mdate=0227093850
6.^ http://www.digitalarchives.wa.gov/governorlocke/bios/bio.htm
7.^ a b Sidoti, Liz (February 25, 2009). "Obama selected Locke to run Commerce Department". Yahoo! News. Associated Press. http://news.yahoo.com/s/ap/20090225/ap_on_go_pr_wh/obama_commerce. Retrieved 2009-02-25. [dead link]

More:

http://en.wikipedia.org/wiki/Gary_Locke