See Defoe's letters, ed. by G. H. Healey (1955); biographies by J. R. Sutherland (2d ed. 1950), J. R. Moore (1958), and J. Richetti (1987); studies by G. H. Starr (1965 and 1971), J. R. Sutherland (1971), P. Rogers, ed. (1972), L. A. Curtis (1984), and P. R. Backscheider (1986).