Concerted Effort | Magic: The Gathering
Formats Concerted Effort is Legal in
Official Oracle Text for Concerted Effort
Official Rulings for Concerted Effort
10/1/2005 : Creatures keep all abilities granted this way until the end of the turn, even if Concerted Effort or the original creature with that ability leaves the battlefield.
5/1/2006 : In Two-Headed Giant, triggers only once per upkeep, not once for each player.