http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
also his Cato Major, and essay on old age; Laelius, an essay on friendship; Paradoxes; Scipio's dream; and letter to Quintus on the duties of a magistrate, literally translated, with notes, designed to exhibit a comparative view of the opinions of Cicero, and those of modern moralists and ethical philosophers