Walker, Edward Everett, 1900-1974
Charles Scribner's Sons, 1943
Buku Teks
Boyd, Anne Morris
H.W. Wilson, 1949
Buku Teks SO
Kamerman, Sheila B.
Temple University Press, 1976
Buku Teks
Metzger, Daniel L.
Prentice-Hall, 1983
Buku Teks
The America University, [date of publication not identified]
Buku Teks