CrossRef

http://www.doi.org/about_the_doi.html 
http://libraryfaq.nd.edu.au/questions/85/ 
http://www.crossref.org/01company/06publishers.html 
http://ilmukomputer.org/2008/11/25/pengantar-xml/ 
http://www.theceli.com/dokumen/produk/pp/1991/70-1991.htm 
http://www.webopedia.com/TERM/D/database.html