Dickey, Albert Venn, 1835-1922, author
Macmillan, 1948
Buku Teks
Thomas, David, author
Penguin Books, 1963
Buku Teks
Artikel Jurnal
Hurst, James Willard
The University of Wisconsin Press, 1956
Buku Teks
Rybczynski, Witold
Simon & Schuster, 1999
Buku Teks