Libero De Rienzo's character name (Dante Cruciani) is a reference to the character that Totò played in Soliti ignoti, I (1958). In that movie, Dante was the safe box expert supposed to train the gang for the robbery.
'Ugo Conti''s hotel room is number 1138. This is a reference to THX1138, George Lucas' first movie, to which Lucas refers to in each of his successive movies.