Dube, Leela, author
Sage, 2001
Buku Teks
edited by Andreas Bandak and Lars Hojer
John Wiley & Sons, 2015
Buku Teks
edited by Donald D. Wood
Emerald, 2016
eBooks
Hollander, Stanley C., author
Michigan State University , 1960
Buku Teks
Willis, James F., author
North West Publishing, 2002
Buku Teks