Artikel Jurnal
M. Hawin, author
Gadjah Mada University Press, 2010
Buku Teks
Frankel, Susy, author
USA Edward Elgar Publishing, 2016
Buku Teks
Edenborough, Michael
Cavendish Publishing , 1994
Buku Teks
Stim, Richard, author
West Thomson Learning, 2001
Buku Referensi