1. Academos LLC. 2005. “Sim teacher”. http://www.simteacher.com/index.html(accessed July 30, 2006)
2. Dispensing with the Fixed Point: Scientific Law as Historical Event
3. Ayers , E. 1999. “The pasts and futures of digital history”. http://www.vcdh.virginia.edu/PastsFutures.html(accessed October 10, 2007)
4. Ayers , E. 2007. “The valley of the shadow”. http://valley.vcdh.virginia.edu(accessed October 12, 2007)