Ott, Bill, author
[American Management Association;, ], 2009
eBooks
Wachlin, Steven, author
KITLV Press, 1994
Buku Referensi
Page, Stephen J.
Royutledge, 1995
Buku Teks
Lazarsfeld, Paul F., author
Amo Press, 1971
Buku Teks
Page, Geoff
Angus & Robertson, 1988
Buku Teks