Manley, John F.
Macmillan, 1976
Buku Teks SO
Isaacs, Asher, 1902-1963
Van Nostrand , 1964
Buku Teks SO
Palumbo, Dennis J.
Harcourt Brace College, 1994
Buku Teks SO
by James W. Ceaser ... [and others]
McGraw-Hill , 1984
Buku Teks SO
Sharkansky, Ira
Rand McNally College Publishing, 1975
Buku Teks