Abdur Rizky Akbar, author
Fakultas Ilmu Sosial dan Ilmu Politik Universitas Indonesia, 2019
UI - Skripsi Membership
Hyland, Ken, author
Longman, 2002
Buku Teks
SAGE publications, 2010
Buku Teks
Katula, Richard A., author
Little, Brown and Company, 1983
Buku Teks
edited by James Flood, Shirley Brice Heath, and Diane Lapp
MacMillan Library Reference USA, 1996
Buku Referensi