A collection of letters by Cicero along with his work on Old Age and On Friendship as well as some letters by Pliny.
Letters of Marcus Tullius Cicero
The Complete Harvard Classics Shelf: 51 Volumes of Essential Classics + 20 Volumes of the Greatest Works of Fiction
Laelius de amicitia
The Letters of Cicero, Volume 1
Cicero's Tusculan Disputations
Harvard Classics: Complete 51-Volume Anthology