Garden City Books, [date of publication not identified]
Buku Referensi
Snyder, Houis L.
Princeton University Press, 1964
Buku Teks
Mende, Tibor
The Noonday Press, 1953
Buku Teks
Keyfitz, Nathan, author
The University of Chicago Press, 1968
Buku Teks
Gilbert, Martin, author
Routledge, 1994
Buku Teks