Graebner, Norman A., author
McGraw-Hill, 1975
Buku Teks
Bailey, Thomas Andrew, 1902-1983, author
D.C. Health, 1983
Buku Teks
Alden, John Richard, author
American Book Company, 1960
Buku Teks
Gabriel, Ralph Henry, 1890-1987, author
D. Appleton-Century, 1942
Buku Teks
Herget, James E., author
Rice University Press, 1990
Buku Referensi