Tannenbaum, Donald G., author
Wadsworth/Thomson learning, 2004
Buku Teks
THe Free Press, 1961
Buku Teks
Corbett, Sister Thomas Albert
University of America Press, 1950
Buku Teks
Koln Westdeutscher 1969
Buku Teks
Schumaker, Paul, author
Blackwell Publishing, 2008
Buku Teks