We show that the Markov semigroups constructed by Misra, Prigogine, and Courbage through nonunitary similarity
transformations of Kolmogorov systems are not implementable by local point transformations, i.e., they
are not the Frobenius-Perron semigroups associated with noninvertible point trans- formations, in contrast
with the semigroups obtained by coarse-graining projections.