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http://en.wikipedia.org/wiki/Spectator_sport
http://www.livescience.com/42220-heart-rate-monitors.html
http://www.livestrong.com/article/396827-the-first-heart-rate-monitor-invented/
http://www.theroar.com.au/2013/08/24/ten-innovations-that-made-rugby-league-and-some-that-didnt/
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http://en.wikipedia.org/wiki/Football_boot
http://www.nma.gov.au/exhibitions/league_of_legends/the_exhibition