Aikens, C. Harold, author
Pearson/Prentice Hall, 2006
Buku Teks
by Greg Bounds [and others]
McGraw-Hill, 1994
Buku Teks
Tarigan, Rostiana, author
Fakultas Ilmu Sosial dan Ilmu Politik Universitas Indonesia, 2005
UI - Tesis (Membership)
Goetsch, David L., author
Pearson, 2016
Buku Teks
by Dale H. Besterfield ... [and others]
Prentice-Hall, 1995
Buku Teks