Beamer and Bibliography

[Wolfgang Engelmann]

I have a Bib.bib file (using Jabref) and would like to add it in the 
last beamer frame. I inserted Bibtex generated Bibliography by using 
Insert > List/Toc > Bib(LA)Tex Bibliography There are about 20 citations 
in the presentation, which are shown in the frames, but only 5 are shown 
on the last frame called References. What has to be done to show all of 
the references? I am using \usetheme[left,width=3.3em]{Berkeley}

Wolfgang