Islam, Syed Serajul, author
Thomson, 2005
Buku Teks
Somit, Albert
Dryden Press, 1974
Buku Teks
edited David Marsh and Gerry Stoker
Macmillan, 1995
Buku Teks
Dyke, Vernon van, author
Stanford University Press, 1962
Buku Teks
Rodee, Carlton Clymer, author
McGraw-Hill, 1983
Buku Teks