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
Organization - Roman Taxation
As to administration in chief, the territories newly acquired by the governor of Narbonese Gaul remained for the time being united with the province of Narbo; it was not till Caesar gave up this office (710) that two new governorships--Gaul proper and Belgica--were formed out of the territory which he conquered. That the individual cantons lost their political independence, was implied in the very nature of conquest. They became throughout tributary to the Roman community. Their system of tribute however was, of course, not that by means of which the nobles and financial aristocracy turned Asia to profitable account; but, as was the case in Spain, a tribute fixed once for all was imposed on each individual community, and the levying of it was left to itself.
In this way forty million sesterces (400,000 pounds) flowed annually from Gaul into the chests of the Roman government; which, no doubt, undertook in return the cost of defending the frontier of the Rhine. Moreover, the masses of gold accumulated in the temples of the gods and the treasuries of the grandees found their way, as a matter of course, to Rome; when Caesar offered his Gallic gold throughout the Roman empire and brought such masses of it at once into the money market that gold as compared with silver fell about 25 per cent, we may guess what sums Gaul lost through the war.
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Reference address : https://www.ellopos.net/elpenor/rome/5-07-subjugation-west.asp?pg=135