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
A more important part in the Romanic development of the west was reserved by destiny for the country which stretches between the Pyrenees and the Rhine, the Mediterranean and the Atlantic Ocean, and which since the Augustan age has been especially designated by the name of the land of the Celts--Gallia--although strictly speaking the land of the Celts was partly narrower, partly much more extensive, and the country so called never formed a national unity, and did not form a political unity before Augustus. For this very reason it is not easy to present a clear picture of the very heterogeneous state of things which Caesar encountered on his arrival there in 696.
The Roman Province - Wars and Revolts There
In the region on the Mediterranean, which, embracing approximately Languedoc on the west of the Rhone, on the east Dauphine and Provence, had been for sixty years a Roman province, the Roman arms had seldom been at rest since the Cimbrian invasion which had swept over it. In 664 Gaius Caelius had fought with the Salyes about Aquae Sextiae, and in 674 Gaius Flaccus,(2) on his march to Spain, with other Celtic nations.
2. Cf. IV. IX. Spain
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Reference address : https://www.ellopos.net/elpenor/rome/5-07-subjugation-west.asp?pg=6