Hawkins, David E.
Palgrave Macmillan, 2006
Buku Teks
Norris, Gweneth
CIMA Publishing, 2005
Buku Teks
Norris, Gweneth
CIMA Publishing, 2005
Buku Teks
Gossling, Tobias
Edward Elgar, 2011
Buku Teks
Wulandari Sukarno Putri
Universitas Indonesia, 2013
UI - Skripsi (Membership)