Question: When did Isabella, Countess Of Vertus's husband die?
Sentence (from "Isabella, Countess of Vertus"): Isabella of France (1 October 1348 – 11 September 1373) was a French princess and member of the House of Valois, as well as the wife of Gian Galeazzo Visconti, who after her death became Duke of Milan.
Relevant evidence: Yes