Ewen, David
Prentice-Hall, 1989
Buku Referensi
Ewen, David
Prentice-Hall, 1952
Buku Teks SO
edited by E.M. Kirkpatrick ; assistant editors, C.M. Schwarz ... [and others]
Chambers, 1983
Buku Referensi
Carlson, Paul A.
South Western, 1957
Buku Teks
edited by Sabine Thiel-Siling ; with contributions by Wolfgang Bachmann ... [and others]
Preste, 1998
Buku Teks SO