Complex sentence: He mentions a (non-extant) work which he wrote, before the "Cronica", on the miracles of Saint Robert of Bury, a boy found murdered in 1181 whose death during a period of rising anti-Semitism was blamed on the local Jews.
Split into simpler sentences: He mentions a (non-extant) work which he wrote, before the "Cronica", on the miracles of St. Robert of Bury. St. Robert of Bury was a boy found murdered in 1181 whose death during a period of rising anti-Semitism was blamed on the local Jews.