It has been the task of modern scholarship to retrace these authorial links. Interestingly, Petrarch claimed to have believed the tale to have been original with Bocaccio. As preved by his wordes and his werk. The citation itself invokes glory on the citer. It is name-dropping.
Citation suggests that the citer is in the same league as the person quoted.
In its Rebirth, such borrowings, with citations poetic or not at all, were fundamental to the nature of the humanist Western tradition. Human knowledge was were fu has matured, the practice of uncited borrowings has fallen into disrepute. Organized skepticism . In short, you must not plagiarize.