http://www.yaxoo.com/Books
http://www.intelligentedu.com/free_computer_books.html
http://leon83.com/download/book/FreeBookList.htm#p
http://webpages.charter.net/akah/knowledge
http://gd.tuwien.ac.at/study
http://www.123aspx.com/Directory.aspx?dir=183
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