1. Ultrarunning 2013—the year in review;Anonymous;UltraRunning,2014
2. Running USA. Running USA annual marathon report. 2014. Available at: http://www.runningusa.org/marathon-report-2014?returnTo=annual-reports. Accessed December 11, 2014.
3. Historical analysis of participation in 161 km ultramarathons in North America;Hoffman;Int J Hist Sport,2010
4. Year in review;Medinger;UltraRunning,2015
5. David GC, Lehecka N. The spirit of the trail: culture, popularity and prize money in ultramarathoning. Available at: http://www.uta.edu/huma/agger/fastcapitalism/10_1/david_lehecka10_1.html. Accessed January 7, 2014.