The books of the Pontiffs are known only through scattered passages preserved throughout Latin literature. Varro is assumed to have drawn on direct knowledge of the lists in writing his now-fragmentary theological books, which were used as a reference by the Church Fathers for their mocking catalogues of minor deities. As William Warde Fowler noted,
the good Fathers tumbled the whole collection about sadly in their search for material for their mockery, having no historical or scientific object in view; with the result that it now resembles the bits of glass in a kaleidoscope, and can no longer be re-arranged on the original Varronian plan.
Georg Wissowa, however, asserted that Varro's lists were not indigitamenta, but di certi, gods whose function could still be identified with certainty, since by the late Republic some of the most archaic deities of the Roman pantheon were not widely cultivated and understood. Another likely source for the patristic catalogues is the lost work De indigitamentis of Granius Flaccus, Varro's contemporary.
W.H. Roscher collated the standard modern list of indigitamenta, though other scholars may differ with him on some points.