Cook, Fred J., author
Encyclopaedia Britannica Press, 1961
Buku Teks
Schlesinger, Arthur Meier, author
Houghton Mifflin, 1960
Buku Teks
Sherwood, Robert T.
Harper & Brothers, 1948
Buku Teks
Lorant, Stepan
N.Y,Simon and Schuster, 1950
Buku Teks
Sherwood, Robert E., author
Bantam Books, 1950
Buku Teks