Hughes, Edward, author
Longman, 1991
Buku Teks
Hughes, Edward, author
Pearson Education, 2002
Buku Teks
Mancer, Clifford J.
The Law Book Company Limited, 1994
Buku Teks
Schonberger, Richard John, author
Business Publications , 1981
Buku Teks
University of Chicago, 1970
Buku Teks