Hospers, John, author
Roudledge, 1988
Buku Teks
Cornman, James W., author
Macmillan, 1968
Buku Teks
Taylor, Paul C., author
Polity Press, 2013
Buku Teks
Angle, Stephen C., author
Polity Press, 2017
Buku Teks
Urmson, J.O., author
Clarendon Press, 1960
Buku Teks