Simonds, John Ormsbee
McGraw-Hill, 1994
Buku Teks
Simonds, John Ormsbee
McGraw-Hill , 1994
Buku Teks
Reina Restianti Amin
2014
UI - Skripsi (Membership)
Lestari Rahayu
Universitas Indonesia, 1997
UI - Laporan Penelitian
Thompson, Elspeth
Page One Publishing , 2002
Buku Referensi