Reference to additional permanent concussion substitutions is found in:

The provision as it is printed, and everything on Ruleside that turns on it.

· The opposing team is informed by the referee/fourth official that it has the option of using an ‘additional substitute' and an ‘additional substitution' opportunity, which may be used concurrently with the ‘concussion substitution' made by the other team or at any time thereafter (except as outlined otherwise in the Laws of the Game).

The Laws of the Game are published by The IFAB and quoted here for the purpose of explaining the decisions on this site. Ruleside is not affiliated with The IFAB or FIFA. Every clause of Notes and modifications that Ruleside cites.