edited by Don E. Hadwiger and Ross B Talbot
Academy of Political Science, 1982
Buku Teks
Helmberger, Peter G., author
McGraw-Hill, 1991
Buku Teks
Hopkins, John A., author
Iowa State University Press, 1962
Buku Teks
Sturrock, Ford, author
Pitman, 1982
Buku Teks
Allen, Frederick Lewis
Bantam Books, 1961
Buku Teks