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.
Available to UK users only.