Sage Publications, 1980
Buku Teks
Rossi, Peter H., editor
Sage Publications, 1980
Buku Teks
by E. Wight Bakke [and others]
John Wiley & Sons, 1954
Buku Teks
edited by Don E. Hadwiger and Ross B Talbot
Academy of Political Science, 1982
Buku Teks
Cambridge University Press, 2004
Buku Teks