Testimonianze
- Alfieri (1976b)
- Allason (1961f)
- Baldini (1961)
- Bargellini (1956)
- Bertolucci (2000a)
- Bianciotto (1977)
- Billanovich (1996)
- Bishop (1900)
- Blum (2000b)
- Cecchi-Praz (1923)
- Contini (1989a)
- Dazzi (1956)
- Fornari (1874)
- Gallino (2001)
- Guccini (2010c)
- Levi (1975b)
- Levi-Montalcini (1987)
- Martini (1880-1912)
- Muñoz (1960)
- Nalli (1940)
- Papini (1913a)
- Pasquali (1929a)
- Pintor-Gentile (1904)
- Prezzolini-Croce (1910)
- Ridolfi (1957)
- Rossanda (2005d)
- Valera (1913)
- Venturi, Franco (1969)
- Verdone (2003a)