edited by Marios Sotiriadis, Dogan Gursoy
Emerald, 2016
eBooks
edited by Metin Kozak, Juergen Gnoth and Luisa Andreu
Routledge, 2010
Buku Teks
Page, Stephen J.
Elsevier , 2009
Buku Teks
edited by Tensie Whelan; foreword by Peter A. A. Berle
New York : Uslan Press, 1991,
Buku Referensi
Boniface, Priscilla, author
Routledge, 1995
Buku Teks