Entwistle, Jill
New York Roto vision SA 1999,
Buku Referensi
Entwistle, Jill
Roto Vision SA, 2000
Buku Referensi
Sobel, Michael I.
University of Chicago, 1987
Buku Teks
Mueller, Conrad G.
Time Incoporated, 1966
Buku Teks
Supriyanto
Universitas Indonesia, 1992
UI - Tesis (Membership)