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
All of these tribes retained, as these legends clearly show, a vivid sense of their relationship and of their having come forth from the Sabine land. While the Umbrians succumbed in the unequal struggle and the western offshoots of the same stock became amalgamated with the Latin or Greek population, the Sabellian tribes prospered in the seclusion of their distant mountain land, equally remote from collision with the Etruscans, the Latins, and the Greeks.
There was little or no development of an urban life amongst them; their geographical position almost wholly precluded them from engaging in commercial intercourse, and the mountain-tops and strongholds sufficed for the necessities of defence, while the husbandmen continued to dwell in open hamlets or wherever each found the well-spring and the forest or pasture that he desired. In such circumstances their constitution remained stationary; like the similarly situated Arcadians in Greece, their communities never became incorporated into a single state; at the utmost they only formed confederacies more or less loosely connected.
In the Abruzzi especially, the strict seclusion of the mountain valleys seems to have debarred the several cantons from intercourse either with each other or with the outer world. They maintained but little connection with each other and continued to live in complete isolation from the rest of Italy; and in consequence, notwithstanding the bravery of their inhabitants, they exercised less influence than any other portion of the Italian nation on the development of the history of the peninsula.
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Reference address : https://www.ellopos.net/elpenor/rome/1-08-umbro-sabellian-samnites.asp?pg=6