Arduino DUE JR1 unidentified on schematic

The Aref circuit shows a object called JR1, but I can't find info on what that is. Also, what value does BR1 have? In fact entire Aref circuit is a mystery to me, where on DUE board is BR1, I read somewhere I should remove it if providing my own Aref.

And is Aref limited to 3.3v on DUE?

I cannot find it either it may be part of that 4 pin header just above PWMVH (10 pin header) I sure would like Arduino to supply a component placement drawing. How about it Arduino?

Looks like this thread should provide an answer...