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http://www.scienceinschool.org/print/1074
http://books.google.com/books?id=Io-rCi0DET0C&pg=PA119&dq=importancia+de+la+ureasa&hl=es&ei=QTH0TYP9M5S_gQeb9tjDCw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CDQQ6AEwAg#v=onepage&q=importancia%20de%20la%20ureasa&f=false blog
http://books.google.com/books?id=nul5vDjLjloC&pg=PA49&dq=importancia+de+la+ureasa&hl=es&ei=sjL0TaaREcbOgAe_kcjuCw&sa=X&oi=book_result&ct=result&resnum=7&ved=0CEoQ6AEwBg#v=onepage&q=importancia%20de%20la%20ureasa&f=false
