Artikel Jurnal
Panjaitan, Alda Mayo Panajam
Universitas Indonesia, 2012
UI - Skripsi (Open)
Robertson QC, Geoffrey
Penguin Books, 2000
Buku Teks
May, Larry
Cambridge University Press, 2005
Buku Teks
Wara Triwardhani
Fakultas Teknik Universitas Indonesia, 2005
UI - Skripsi (Membership)