Keyfitz, Nathan, author
The University of Chicago Press, 1968
Buku Teks
Borrie, W.B., author
Weidenfeld and Nicolson, 1970
Buku Teks
Population Reference Bureau, Inc., 1972
Buku Teks
Voice of America, U.S. Information Agency, 1969
Buku Teks
National Academy of Sciences-National Research Council , 1963
Buku Teks