31.5.2001

In my paper I overlooked the important references:

Brosowski, B., \"Uber die Eindeutigkeit der rationalen
Tschebyscheff-Approxim\-ationen, {\sl Numer.~Math.} {\bf 7}
(1965), 176--186.

Brosowski, B. and Stoer, J., Zur rationalen
Tschebyscheff-Approximation differenzierbarer und analytischer
Funktionen, {\sl Numer.~Math.} {\bf 12} (1968), 57--65.

In particular, in the first of these references it is proven that
$U_n/V_m$ is a unicity set if and only if $U_n + r^*V_m$ is a Haar
space for every $r^* \in U_n/V_m$. In my paper only one
direction is mentioned.

Note also that the main question of the paper still remains open.
That is, what are necessary and sufficient condtions on $U_n$ and
$V_m$ so that $U_n/V_m$ is a unicity set (or that $U_n + r^*V_m$
is a Haar space for every $r^*\in U_n/V_m$). In this paper we
provide sufficient conditions which we believe to also be
necessary.