Cross, Harry, author
Policy Project, 2002
Buku Teks
Hans Groth
Springer, 2012
eBooks
Coale, Ansley J., author
Princeton University Press, 1958
Buku Teks
Clarke, John I., author
Pergamon Press, 1979
Buku Teks
Cuca, Roberto, author
John Hopkins University Press, 1977
Buku Teks