Taylor, Overton H.
Kogakusha Company,Ltd., 1960
Buku Teks
Roll, Eric
Prentice-Hall, 1959
Buku Teks
Fusfeld, Daniel Roland, 1922-, editor
Scott, Foresman and Company, 1986
Buku Teks
Beaud, Michel
Routledge , 1997
Buku Teks
Haney, Lewis H., author
Macmillan, 1949
Buku Teks