Rose, Leo E.
Cornell University Press, 1970
Buku Teks
Wang, James C.F., author
Prentice-Hall, 1994
Buku Teks
Merriam, Charles E. (Charles Edward), author
New York University Press, 1936
Buku Teks
Solomos, John, author
Routledge, 1995
Buku Teks
Gilpin, Robert, author
Cambridge University Press, 1981
Buku Teks