Coffey, Amanda, author
Open University Press, 2004
Buku Teks
MacIver, Robert M., author
Macmillan, 1951
Buku Teks
Julien Masanes
Springer, 2006
Buku Teks
Behrman, Daniel, author
UNESCO, 1964
Buku Teks
Kaplan, Howard B., author
Sage Publications, 1984
Buku Teks