  Luo et al. proposed a new method to design the maximally permissive and
efficient supervisor for enforcing linear constraints on an ordinary Petri net
with uncontrollable transitions. In order to develop this method, Theorem 3 is
given. It is claimed that 'a linear constraint can be equivalently transformed
at an uncontrollable transition into a disjunction of weakly admissible ones.'
However, this result is erroneous. In this correspondence paper, a
counterexample contradicting it is presented.
