Forrest, Joshua B., author
Westview Press, 1992
Buku Teks
Duchacek, Ivo D., author
Holt, Rinehart and Winston, 1965
Buku Teks
Emerson, Rupert, author
Cambridge: Harvard University Press, 1960
Buku Teks
Banton Michael, author
Oxford University Press, 1957
Buku Teks
Cleary, Joe, author
Cambridge University Press, 2009
eBooks