Citazione Stile APA (7a Edizione)

Sumner, W. G., & Keller, A. G. (1914). The challenge of facts, and other essays. Yale University Press.

Citazione stile Chigago Style (17a edizione)

Sumner, William Graham, e Albert Galloway Keller. The Challenge of Facts, and Other Essays. New Haven: Yale University Press, 1914.

Citatione MLA (9a ed.)

Sumner, William Graham, e Albert Galloway Keller. The Challenge of Facts, and Other Essays. Yale University Press, 1914.