usepackage[spanish]{babel}
usepackage{natbib}
...
begin{document}
...
...
...

%-----------------------------------
%   BIBLIOGRAPHY
%-----------------------------------

label{Bibliography}
lhead{textsc{Bibliograf'ia}} % Change the page header to say "Bibliography"
bibliographystyle{dcu} % Use the "dcu" BibTeX style for formatting the Bibliography
nocite*{}
bibliography{Bibliography.bib} % The references (bibliography) information are stored in the file named "Bibliography.bib"

end{document}