Artikel Jurnal
Lewis, Norman, author
Harper & Row , 1962
Buku Referensi
Chamberlin, Marry W., author
American Library Association, 1959
Buku Referensi
Borland International, 1988
Buku Referensi
editors, Richard C. Johnson, Henry Jasik
McGraw-Hill, 1987
Buku Referensi