VELLEIUS PATERCULUS, History of Rome
[II.XCV] Reuersum inde Neronem Caesar haud mediocris belli mole experiri statuit, adiutore operis dato fratre ipsius Druso Claudio, quem intra Caesaris penates enixa erat Liuia. Quippe uterque, diuisis partibus, Raetos Vindelicosque adgressi, multis urbium et castellorum oppugnationibus nec non derecta quoque acie feliciter functi gentes locis tutissimas, aditu difficillimas, numero frequentes, feritate truces maiore cum periculo quam damno Romani exercitus, plurimo cum earum sanguine perdomuerunt. Ante quae tempora censura Planci et Pauli acta inter discordiam neque ipsis honori neque rei publicae usui fuerat, cum alteri uis censoria, alteri uita deesset, Paulus uix posset implere censorem, Plancus timere deberet, nec quidquam obiicere posset adulescentibus aut obiicientes audire quod non agnosceret senex.
[2.95] On Tiberius' return Caesar resolved to test his powers in a war of no slight magnitude. In this work he gave him as collaborator his own brother Drusus Claudius, to whom Livia gave birth when already in the house of Caesar. The two brothers attacked the Raetii and the Vindelici from different directions, and after storming many towns and strongholds, as well as engaging successfully in pitched battles, with more danger than real loss to the Roman army, though with much bloodshed on the part of the enemy, they thoroughly subdued these races, protected as they were by the nature of the country, difficult of access, strong in numbers, and fiercely warlike. Before this had occurred the censorship of Plancus and Paulus, which, exercised as it was with mutual discord was little credit to themselves or little benefit to the state, for the one lacked the force, the other the character, in keeping with the office; Paulus was scarcely capable of filling the censor's office, while Plancus had only too much reason to fear it; nor was there any charge which he could make against young men, or hear others make, of which he, old though he was, could not recognize himself as guilty.