 In a further letter to Somma a month later (after he had re-read the play), Verdi detailed his concept of how the opera should be constructed.As documented in their extensive correspondence and with Verdi's overally detailed supervision, two completed and still extant versions of the libretto were prepared, the first in 1853 followed by the second in 1855.Only in 1996 did music historian Leo Karl Gerhartz come across a brief paper in the Carrara-Verdi archives at Sant' Agata, Verdi's home near Busseto, and it was through the later support from that family (as well as the American National Endowment for the Humanities) that much more material including Somma's manuscript libretto became available on microfilm.