Conklin, Harold C., author
University of California Press, 1953
Buku Referensi
Bauer, Lauria
London : Routledge, 1998
Buku Teks
Morgan, John, 1944-2004, author
Oxford University Press, 1990
Buku Teks SO
Buku Teks
Read, John, author
Cambridge University Press, 2000
Buku Teks