Stably tame coordinates

In this paper, a class of polynomials in 2 variables is introduced which, in the field case, exactly describes all coordinates in 2 variables. In particular, all of those coordinates are tame. But viewing these polynomials over an arbitrary commutative ring, they are not always coordinates; and when they are, they are usually not tame. But here we will prove, that all of these coordinates are stably tame.