Brenkert, G. G. (1991). Political freedom. Routledge.
Cita Chicago (17th ed.)Brenkert, George G. Political Freedom. London: Routledge, 1991.
Cita MLA (9th ed.)Brenkert, George G. Political Freedom. Routledge, 1991.
Atenció: Aquestes cites poden no estar 100% correctes.