Insko, Chester A.
Prentice Hall Inc., 1967
Buku Teks
Leece, Sharon, author
Periplus, 2003
Buku Teks
Bernard, Chester I., author
Harvard University Press , 1948
Buku Teks
Brandt, Willy, author
Verlag Neue Gesellschaft , 1971
Buku Teks
Kyung Hee Univerity Press, [date of publication not identified]
Buku Teks