Naisbitt, John, author
Pan Books, 1990
Buku Teks
Fox-Rushby, Julia A., author
Office of Health Economics, 2002
Buku Teks
Naisbitt, John, author
Simon & Schuster, 1996
Buku Teks
Gallup, George, author
McGraw-Hill, 1982
Buku Teks
Lin, Yutang, author
Prentice-Hall, 1955
Buku Teks