Ellis, Rob
Blackwell, 1990
Buku Teks
Leaver, Betty Lou
Cambridge Press , 2005
Buku Teks SO
Mitchell, Rosamond
Arnold, 1998
Buku Teks SO
Hummel, Kirsten M.
Wiley Balckwell, 2014
Buku Teks SO
edited by Jessica Williams and Bill Van Patten
NY : Routledge, 2015
Buku Teks SO