Aini, Sadridin
Foreign Languages Pub. House, 1958
Buku Teks
Simmons, Annette, author
American Management Association, 2007
eBooks
Koke, Louise G.
January Books, 1987
Buku Teks
Okely, Judith, author
Routledge, 1996
Buku Teks
Sutton, Garrett, author
Warner Books, 2001
Buku Teks