Guerra was prolific and worked with many directors including Fellini, Antonioni and Tarkovsky. The obituary from the Independent is very good:
In 1973 Amarcord (in dialect, "I Remember") was the first of three films with Fellini and one of his most personal, drawing on the two men's memories of their Rimini youths. It brought a third Oscar nomination, though he lost to Dog Day Afternoon. The novelisation appeared under both their names but seems mostly to have been Guerra's work. After Casanova in 1976 Fellini wanted Guerra to write City of Woman but he was wooing a Russian woman at the time and felt it would be impossible as he commuted between Rome and Moscow. But he later returned to work with Fellini on the parable And the Ship Sails On (1983) and the amusing if lightweight Ginger and Fred (1986).