Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
Nevertheless the poem on Morals and the instructions in Oratory, which were found among the writings of Cato, may be regarded as the Roman quintessence or, if the expression be preferred, the Roman -caput mortuum- of Greek philosophy and rhetoric.
The immediate sources whence Cato drew were, in the case of the poem on Morals, presumably the Pythagorean writings on morals (along with, as a matter of course, due commendation of the simple ancestral habits), and, in the case of the book on Oratory, the speeches in Thucydides and more especially the orations of Demosthenes, all of which Cato zealously studied.
Of the spirit of these manuals we may form some idea from the golden oratorical rule, oftener quoted than followed by posterity, "to think of the matter and leave the words to follow from it."(68)
68. -Rem tene, verba sequentur.-
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Reference address : https://www.ellopos.net/elpenor/rome/3-14-literature-art.asp?pg=102