1. National Cancer Institute. Surveillance, Epidemiology, and End Results (SEER) stat fact sheet. 2010. Available at: http://seer.cancer.gov/statfacts/html/all.html.
2. National Transportation Safety Board. Aviation accident statistics. Available at: www.ntsb.gov/aviation/Stats.htm.
3. Bureau of Transportation Statistics. Transportation statistics. 2010. Available at: www.transtats.bts.gov.
4. Travel Industry of America/Bureau Of Transportation Safety a air travel survey results,2002
5. Error in the delivery of radiation therapy: Results of a quality assurance review;Huang;Int J Radiat Oncol Biol Phys,2005