Ultra running

found : Pitt, S. Running to extremes: Ray Zahab's amazing ultramarathon journey, 2011.

found : The Canadian Oxford Dictionary, 1998 p. 1574 (Ultra-marathon - "a running or cycling race over a distance longer than that of a marathon, esp. 50 km, 50 miles, 70 km, or more")

found : SIRCThesaurus: the thesaurus of terminology used in the SPORTDiscus, 2001 p. 213 (Ultramarathon - BT Long distance running, BT Ultraendurance sport)

found : Telegraph UK WWW site, Sept. 2, 2015 (10 things no one tells you before you run an ultra-marathon: You'll laugh, you'll cry, and you'll probably do a fair bit of walking. Damian Hall introduces you to the world of ultra-marathons)

found : IAAF (International Association of Athletics Federations) WWW site, Sept. 2, 2015 (Disciplines: Ultra running: Ultra races are contested over two different types of race modalities, either over a set distance (50km, 100km and longer) or a set time (6hr, 24hr, and multi day events))

found : IAU WWW site, Sept. 2, 2015 (The International Association of Ultrarunners (IAU) is operating under the patronage of the IAAF and is dedicated to develop ultradistance running internationally within the IAAF Rules & Regulations. As international governing body for ultradistance running, one of our main objectives is to promote and develop long distance running worldwide by encouraging specific activities in each of the IAAF Continental Areas)