Theodor Mommsen
In the Augustan division of Italy, however, Placentia belonged to the 8th region, "Aemilia", whereas Iria certainly, and Clastidium possibly, belonged to the 9th region, "Liguria" (see Theodor Mommsen in "Corp. Inscrip. Lat." vol. v. Berlin, 1877, p. 828).