Heany, Donald F.
Ronald Press, 1968
Buku Teks
Silaban, Rumata Marsaulina
Fakultas Ilmu Komputer Universitas Indonesia, 2017
UI - Tugas Akhir
Beynon-Davies, Paul
Palgrave Macmillan, 2002
Buku Teks
Doyle, Lauren B.
John Wiley & Sons, 1975
Buku Teks
Megarry, Jacquetta
British Broadcasting Corporation, 1985
Buku Teks