Usain Bolt's record 40-yard dash puts NFL players to shame
Combine 101: 40-Yard Dash
Evaluating the importance of the 40-yard dash - Cincy Jungle
Alabama's Henry Ruggs wows at NFL combine with 4.27 time in 40 - ESPN
Predicting Football Speed And Success With The 40-Yard Dash
The NFL Combine really doesn't mean a whole lot in the grand scheme of things - Baltimore Beatdown
5 Fastest 40-Yard Dash Times in NFL Combine History