Abstract Two topologies on a set X are called PO-equivalent if their families of preopen sets concide.
Let P(T) stand for the class of all topologies on X which are PO-equivalent to T and denote by
TM the topology on X having for a base Tα∪{{x}∣{x} is closed-and-open in
Tγ}. It was proved in [Andrijević, M. Ganster, \emph{On PO-equivalent topologies},
Suppl. Rend. Circ. Mat. Palermo, {\bf 24} (1990), 251--256] that the class P(T) does not have the largest member in general.
Precisely, if P(T) has the largest member, say U, then U=TM.
On the other hand, it was shown that TM does not necessarily belong to P(T).
In this paper we are going to show that the topology TM is actually the least upper bound of the class~P(T). 
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