What is commotio cordis, which NFL player Damar Hamlin says stopped his heart?
Damar Hamlin: Patrick Mahomes wears special Hamlin Kansas City Chiefs shirt
Hamlin in their hearts, the NFL pays tribute to No. 3
Bills' Hamlin breathing on his own, joins team via video
NFL teams, players show support for Bills safety Damar Hamlin ahead of Week 18 games
NFL Star on a Bills Rival Wears Damar Hamlin Jersey Pregame
Damar Hamlin in their hearts, the NFL pays tribute to No. 3
17) Watch: Hamlin patches get stitched on to Bills jerseys for today's game