Universitas Indonesia, 2005
UI - Skripsi (Membership)
Hutahaean, E.
"Jakarta: Gramedia, 1980",
Buku Teks
Bonic, Robert A.
"Lexington, Massachusetts D C Heath and Co., 1971",
Buku Teks
Ayres, Frank, 1901-1994
Erlangga, 2002
Buku Teks
Purcell, Edwin Joseph, 1901-
Buku Teks