edited by Stefan G. Hofman and Joel Weinberger
Routledge, 2007
Buku Teks
Bono, Edward de, author
Fontana, 1991
Buku Teks
Carnegie, Dale, 1888-1955, author
Dale Carnegie & Associates, 1984
Buku Teks
Visser, H. F. E., author
De Spieghel Publishing, 1947
Buku Referensi
Basmadjian, Diran, author
Chapman & Hall/CRC , 2007
Buku Teks