  J. Berson, J. W. Bikker and A. van den Essen proved that for a
non-zerodivisor $a$ in a commutative ring $R$ containing $Q$ if the polynomials
$f_1,\dots,f_{n-1}$ in $R[X_1,\dots,X_n]$ form a partial coordinate system over
the rings $R_a$ and $\dfrac{R}{aR}$ then $f_1,\dots,f_{n-1}$ form a partial
coordinate system over the ring $R$. In this note we show that the theory of
residual variables of Bhatwadekar-Dutta and its recent extension by Das-Dutta,
extends their result to the case when $a$ is an arbitrary element of $A$.
