Silver, M.S.
Westview Press, 1984
Buku Teks
Wilson, Charles, author
Cassell, 1970
Buku Teks
Fogel, Robert William, author
Johns Hopkins Press, 1964
Buku Teks
Maxensius Tri Sambodo, author
[Publisher not identified], 2012
Artikel Jurnal
Artikel Jurnal