Monroe, James Stewart, 1938-
Wadsworth, 1997
Buku Teks
Butler, B.C.M.
Longman Scientific & Technical , 1988
Buku Teks
Prothero, Donald R.
McGraw-Hill Higher Education, 2004
Buku Referensi
Monroe, James Stewart, 1938-
Brooks/Cole, 2012
Buku Teks
Ward, Dederick C.
Scarecrow Press, 1981
Buku Referensi