Muhammad Shalih al-Munajjid, author
Cakrawala Publishing, 2005
Buku Teks
Robi Wijaya, author
Gramedia Pustaka Utama, 2007
Buku Referensi
Universitas Indonesia, 1985
UI - Skripsi Membership
Rosianti Tita, author
Gagas Media, 2008
Buku Teks
Panjaitan, Novalin Cahaya Difa Elizabeth, author
Fakultas Psikologi Universitas Indonesia, 2010
UI - Skripsi Open