Waite, Mitchell, author
H.W. Sams, 1980
Buku Teks
Stone, Harold S., 1938-, author
Addison-Wesley, 1982
Buku Teks
Seals, Richard C., author
Stanley Thornes, 1993
Buku Teks
Birley, Sue, author
Financial Times Prentice Hall, 2000
Buku Teks
Watson, John, author
Macmillan, 1990
Buku Teks