Sega Ages: John Madden Football – Sega-16
Retro Gamer Randomness: Rare (?) Clamshell Variant of John Madden Football for Sega Genesis
My Favorite 16 Bit Sega Genesis Gridiron Football Games. : r/SEGAGENESIS
The History of Football Games - GameSpot
John Madden Football - A 16-Bit Sega Legacy