Wakefield, Jill, author
Kluwer, 2007
Buku Teks
Surbakti, Ramlan, author
Ministry of Home Affairs R.I., 2000
Buku Teks
Lepawsky, Albert
Alfred A Knopf, 1952
Buku Teks
Hughes, Owen E., author
England Palgrave Macmillan, 2012
Buku Teks
Cayer, N. Joseph, author
Thomson wadsworth, 2004
Buku Teks