 For some episodes, the sources Ovid used are untraceable.On the Roman side, Ovid particularly focuses on and employs Virgil's "Aeneid" and "Eclogues", most notably in the long section on Anna in Book 3.As in the "Metamorphoses", Ovid's use of Virgil is multifaceted; he often prefers to invert or abbreviate Virgil's episodes.