Hanford, James Holly
F.S. Croff & Co., 1946
Buku Teks
Bradford, Richard, 1957-, author
Routledge, 2001
Buku Teks
Heffernan, James A.W.
W.W. Norton & Company, 1986
Buku Teks
edited by W.A. Paton
Ronald Press, 1955
Buku Teks
editor, Harry Helms [and others]
McGraw-Hill, 1983
Buku Referensi