Pallister, Anne, author
Oxford University Press, 1972
Buku Teks
Holt, J.C., author
Cambridge University Press, 1992
Buku Teks
Handlin, Oscar, author
Atheneum, 1966
Buku Teks
Mill, John Stuart, author
David Campbell Publisher, 1992
Buku Referensi
Walker, Patrick Gordon, author
Hutchinson & Company, 1951
Buku Teks