Curtis, B. (1981). William Graham Sumner. Twayne.
Chicago Style (17th ed.) CitationCurtis, Bruce. William Graham Sumner. Boston: Twayne, 1981.
MLA (9th ed.) CitationCurtis, Bruce. William Graham Sumner. Twayne, 1981.
Advarsel: Disse citationer er muligvist ikke 100% nøjagtige.