1. "HOW TO HARNESS COLLECTIVE WISDOM" GOOGLE BOOKS sample //http://books.google.gr/books?id=k3vvYZLBhS8C&printsec=frontcover&dq=alexander+christakis&hl=el&sa=X&ei=Rn2_UJWILNKWhQec2oDQCQ&ved=0CDIQ6AEwAQ//
2. "THE TALKING POINT" GOOGLE BOOKS sample
http://books.google.gr/booksid=GUPk3MC4NPQC&printsec=frontcover&dq=alexander+christakis&hl=el&sa=X&ei=gm3AUOCxD5DLtAbkh4GIAw&ved=0CDUQ6AEwAg#v=onepage&q=alexander%20christakis&f=false