MD : Bernan Press, 2004
Buku Teks
Brown, Everett S.
Appleton-Century-Crofts, Inc., 1950
Buku Teks
Walker, Edward Everett, 1900-1974, author
Charles Scribner's Sons, 1943
Buku Teks
Boyd, Anne Morris, author
H.W. Wilson, 1949
Buku Teks
The America University, [date of publication not identified]
Buku Teks