bibliografia e collegamento ipertestuale file pdf

Problema: il link della table of contents alla bibliografia del file pdf mi “manda” al capitolo conclusioni e non alla bibliografia.
O.

Codice:
`
\documentclass[a4paper,11pt,titlepage]{book}

\usepackage[english,italian]{babel}
\usepackage{front-th}
\usepackage[latin1]{inputenc}
\usepackage{graphicx}
\usepackage[vcentering]{geometry}
\usepackage{fancyhdr}
\usepackage{url}
\usepackage{varioref}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{cases}
\usepackage{subfigure}
\usepackage{textcomp}
\usepackage{enumerate}
\usepackage[pdftex,hypertexnames=false]{hyperref}
\hypersetup{pdftitle=tesi}

\begin{document}

\frontmatter
\include{frontespizio}
\include{dedica}
\include{ringraziamenti}
\clearpage{\pagestyle{empty}\cleardoublepage}
\tableofcontents
\clearpage{\pagestyle{empty}\cleardoublepage}

\begin{mainmatter}
\include{intro}
\include{capitolo1}
\include{capitolo2}
\include{capitolo3}
\include{capitolo4}
\include{conclusioni}
\clearpage{\pagestyle{empty}\cleardoublepage}
\end{mainmatter}

\begin{backmatter}
\addcontentsline{toc}{chapter}{Bibliografia}
\bibliographystyle{plain_ita}
\begin{otherlanguage*}{english}
\clearpage{\pagestyle{empty}\cleardoublepage}
\bibliography{biblio}
\end{otherlanguage*}
\end{backmatter}

\end{document}
`