The libretto has survived in numerous forms—two printed versions, seven manuscript versions or fragments, and an anonymous scenario, or summary, related to the original production. One of the printed editions relates to the opera's 1651 Naples revival; the other is Busenello's final version published in 1656 as part of a collection of his libretti. The manuscripts are all from the 17th century, though not all are specifically dated; some are "literary" versions unrelated to performances. The most significant of the manuscript copies is that discovered in Udine, Northern Italy, in 1997 by Monteverdi scholar Paolo Fabbri. This manuscript, according to music historian Ellen Rosand, "bristles with the immediacy of a performance", and is the only copy of the libretto that mentions Monteverdi by name. This, and other descriptive details missing from other copies, leads Rosand to speculate that the manuscript was copied during the course of a performance. This impression is reinforced, she says, by the inclusion of a paean of praise to the singer (Anna di Valerio according to Schneider) who played the role of Poppea. Although its dating is uncertain, the manuscript's affinity with the original scenario has led to speculation that the Udine version may have been compiled from the first performance.