It should be observed that in the oldest accounts there is no mention of Juventas, whose name (with that of Mars) was added in support of the augural prediction.
The science of augury was contained in various written works, which were consulted as occasion arose: such were the libri augurum, a manual of augural ritual, and the commentarii augurum, a collection of decrees or answers given by the college to the senate in certain definite cases.
In the First Punic War, Caere furnished Rome with corn and provisions, but otherwise, up till the end of the Republic, we only hear of prodigies being observed at Caere and reported at Rome, the Etruscans being especially expert in augural lore.
There were also Commentarii of the priestly colleges: (a) Pontificum, collections of their decrees and responses for future reference, to be distinguished from their Annales, which were historical records, and from their Acta, minutes of their meetings; (b) Augurum, similar collections of augural decrees and responses; (c) Decemvirorum; (d) Fratrum Arvalium.
The opposition between ager Romanus and ager Gabinus in the augural law.