Sumner, W. G. (1952). What social classes owe to each other. Caxton Printers.
Lua i Stíl Chicago (17ú heag.)Sumner, William Graham. What Social Classes Owe to Each Other. Caldwell, Idaho: Caxton Printers, 1952.
Lua MLA (8ú heag.)Sumner, William Graham. What Social Classes Owe to Each Other. Caxton Printers, 1952.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.