Tambunan, Emil H., author
Indonesia Publishing House, 2009
Buku Teks
Linggawati Haryanto, author
Fakultas Psikologi Universitas Indonesia, 2001
UI - Skripsi (Membership)
Chua Amy, author
Gramedia Pustaka Utama, 2011
Buku Teks
Artikel Jurnal
Savitri Ramadhani, author
Smart Books, 2006
Buku Teks