sub for a sub

[euby]

What about 3-3-Art. 4?
A player who has been replaced, or directed to leave the game shall not re-enter before the next opportunity to substitute after the clock has been started properly following his/her replacement.

So what I get out of this is you can't substitute for someone who has already been substituted out. You can however put a different player in.

So if A2 goes in for A1 then A1 has to wait until next opportunity ...however A2 can be replaced by A3 but not A1

OPPS...just saw Bktballref's answer...same thing.