[biblio] Cross-reference within a bibliography

[mario]

Hello


In the biblatex tutorial 
http://www.ctan.org/tex-archive/macros/latex/exptl/biblatex/doc/biblatex.pdf
at pag. 168-169 the author offers a few hint on how to implement a nice
feature to produce cross-reference among records within a
bibliography:  

[1] Audrey Author: Title of article. In: [2], pp. 134–165. 
[2] Edward Editor, ed.: Title of collection. Publisher: Location, 1995.


Since I am not a (La)TeX programmer, I would like very much to hack the
complete code from somewhere/somebody.

I load by 
\usepackage[style=numeric,hyperref=auto,defernums=true,annotation=true,library=true,sorting=nyt]{biblatex}
To cross-reference, I use both the crossref and the Xref fields. 

Thanks very much
regards
mario