Calvin Johnson retired because he was 'fed up' with football
Pat Caputo – Detroit Lions, Calvin Johnson, Matthew Stafford and facts vs. fiction – Daily Tribune
NFL notes: Calvin Johnson tells Lions he's retiring, report says - The Boston Globe
Former Detroit Lions receiver Calvin Johnson says he is content in retirement - ESPN
Detroit Lions star WR Calvin Johnson retires after 9 seasons
Drew Sharp: Leave it to Lions to lose Calvin Johnson
Where is Calvin Johnson now? What the Lions legend is doing after his early 2015 retirement
Calvin Johnson's first social media message in retirement -- pizza - ESPN - Detroit Lions Blog- ESPN
NFL Notebook: Lions' Calvin Johnson retires - West Central Tribune
Calvin Johnson opens up on rift with Lions: 'It straight up stung'
Detroit Lions – Reaction to retirement of Calvin Johnson, a 'humble superstar' – The Oakland Press
In statement, Calvin Johnson to evaluate future with Lions
Calvin Johnson says he learned to play through concussions during his career with the Lions - The Washington Post