Pringle, Henry Fowles, 1897-1958
Harcourt, Brace & World, 1956
Buku Teks SO
Cook, Fred J.
Encyclopaedia Britannica Press, 1961
Buku Teks
Ludwig, Emil, 1881-1948
Garden City Publishing, 1941
Buku Teks SO
Douglas, Helen Gahagan
Hill and Wang, 1963
Buku Teks SO
Dreiser, Theodore
A Premier Book, 1965
Buku Teks SO