There you go pal, a video explaining it, full with references and everything, have fun looking it up.
https://www.youtube.com/watch?v=PRw25KZG0vE
if you want a better video with a better explanation
https://www.youtube.com/watch?v=XPZjDErZIBo
Bradford City Fan for life
Recent favourite games: Ni No Kuni, Fifa 13, Batman Arkham City
Best games of all time: Pokemon Red, Dragon Warrior 3, The last of us, Uncharted 2 and 3
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