Using the "pubblicazione di matrimonio"
Most posts request information but this one offers a tip. My ancestor is the daughter of Maria CASALETTO and Angelo SANGREGORIO in Potenza the city. The husband remarried, and the remarriage record gave his parents' names, but that didn't tell me if he was the same one, because I didn't have anything to compare that with. The remarriage record said he's a widower, but didn't give the name of the deceased wife.
Then I checked the pubblicazione, and it said what documentation he submitted, including the death certificate of his wife, Maria CASALETTO, who died 15 December 1873. This solidly identified him as the same Angelo SANGREGORIO and with that, identified his parents.