Male and female deities are extensively mentioned in the Vedas. The earliest "mandalas" ("Books"; the authorship of each "mandala" is traditionally ascribed to a particular "rishi" or that "rishi"'s family) of the Rigveda, estimated to have been composed sometime in the 2nd millennium BCE, invoke and praise both gods and goddesses. "Ushas" ("Goddess of Dawns") is praised in twenty Hymns of Chapters VI.64, VI.65, VII.78 and X.172, with Hymn VI.64.5 declaring goddess Ushas as the one who must be worshipped first.