Universitas Indonesia, 2014
UI - Skripsi (Membership)
APA Publications , 2007
Buku Referensi
Syarif Awad Umar, author
2015
UI - Skripsi (Membership)
Boniface, Brian G, author
Routledge, 2016
Buku Teks
Hammial, Phillip
Angus & Robertson Publisher, 1989
Buku Teks