  Let R be a PID. We construct and classify all coordinates of R[x,y] of the
form p_2y+Q_2(p_1x+Q_1(y)) with p_1 and p_2 in qt(R) and Q_1 and Q_2 in
qt(R)[y]. From this construction (with R=K[z]) we obtain non tame automorphisms
s of K[x,y,z] (where K is a field of characteristic 0) such that the sub-group
generated by s and the affine automorphisms contains all tame automorphisms.
