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
Marcus Perpenna, who hitherto as the equal of Sertorius in rank had claimed an independent command over the force which he had brought with him from Liguria, was, on the news of the arrival of Pompeius in Spain, compelled by his soldiers to place himself under the orders of his abler colleague.
For the campaign of 678 Sertorius again employed the corps of Hirtuleius against Metellus, while Perpenna with a strong army took up his position along the lower course of the Ebro to prevent Pompeius from crossing the river, if he should march, as was to be expected, in a southerly direction with the view of effecting a junction with Metellus, and along the coast for the sake of procuring supplies for his troops.
The corps of Gaius Herennius was destined to the immediate support of Perpenna; farther inland on the upper Ebro, Sertorius in person prosecuted meanwhile the subjugation of several districts friendly to Rome, and held himself at the same time ready to hasten according to circumstances to the aid of Perpenna or Hirtuleius. It was still his intention to avoid any pitched battle, and to annoy the enemy by petty conflicts and cutting off supplies.
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Reference address : https://www.ellopos.net/elpenor/rome/5-01-lepidus-sertorius.asp?pg=43