Holt, J.C.
Cambridge University Press, 1992
Buku Teks
Handlin, Oscar
Atheneum, 1966
Buku Teks
Mill, John Stuart
David Campbell Publisher, 1992
Buku Referensi
Walker, Patrick Gordon
Hutchinson & Company, 1951
Buku Teks
Jones, J.A.P.
Longman, 1971
Buku Teks