Hale & Ireminger, 1992
Buku Teks
Dubois, Brenda, 1949-, author
Allyn and Boston, 1992
Buku Teks
Fellin, Phillip, author
Thomson, 2001
Buku Teks
Coulshed, Veronica, author
Macmillan, 1988
Buku Teks
Cohen, Nathan Edward, author
National Ass. of Workker, 1964
Buku Teks