World Athletics 2013: The battle with doping in athletics

BBC athletics reporter Phil Jones examines how the spectre of doping continues to haunt the sport.

Usain Bolt, Lord Coe and IAAF Vice-President Sergey Bubka are among those who give their views on the sport's battle against drugs cheats.

The athletics world has been rocked by a series of doping scandals in recent weeks, with sprint stars Tyson Gay and Asafa Powell among those testing positive for banned substances.

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