Dahl, Robert A., 1915-2014
Prentice-Hall, 1978
Buku Teks
Sankar Muthu
Cambridge University Press, 2014
Buku Teks
Routledge, 2000
Buku Teks
edited by Robert E. Ward
Princeton University Press, 1968
Buku Teks
editors, Robert E. Ward and Roy C. Macridis
Prentice-Hall, 1963
Buku Teks