Kubasek, Nancy K.
Pearson - Prentice Hall, 2005
Buku Teks
McCaffrey, Stephen C.
Thomson/West, 2009
Buku Teks
Doelle, Meinhard
Carswell, 2009
Buku Teks
Kiss, Alexandre Charles, 1925-
Grotius Publications Limited, 1993
Buku Referensi
Findley, Roger W.
West Publishing, 1983
Buku Teks