APA (7th ed.) Citation

Lewis, C. S., Juan Calabria, S., & Moynihan, M. (1989). Letters C.S. Lewis Don Giovanni Calabria: A study in friendship. Collins.

Chicago Style (17th ed.) Citation

Lewis, C. S., Santo Juan Calabria, and Martin Moynihan. Letters C.S. Lewis Don Giovanni Calabria: A Study in Friendship. London: Collins, 1989.

MLA (9th ed.) Citation

Lewis, C. S., et al. Letters C.S. Lewis Don Giovanni Calabria: A Study in Friendship. Collins, 1989.