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
Transpadanes - Freedmen
But, above all, efforts were made to complete the democratic restoration and to realize the leading ideas of the Gracchan period in a form suitable to the times. The election of the priests by the comitia, which Gnaeus Domitius had introduced(2) and Sulla had again done away,(3) was established by a law of the tribune of the people Titus Labienus in 691.
2. Cf. IV. VI. Political Projects of Marius
3. Cf. IV. X. Co-optation Restored in the Priestly Colleges
The democrats were fond of pointing out how much was still wanting towards the restoration of the Sempronian corn-laws in their full extent, and at the same time passed over in silence the fact that under the altered circumstances--with the straitened condition of the public finances and the great increase in the number of fully-privileged Roman citizens--that restoration was absolutely impracticable. In the country between the Po and the Alps they zealously fostered the agitation for political equality with the Italians.
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Reference address : https://www.ellopos.net/elpenor/rome/5-05-parties-pompeius.asp?pg=6