Agglutination in Old Irish

On another list, Michael Everson wrote:
>
> Peter T. Daniels wrote:
> >
> > So you've identified a feature that separates the branches
> > of Italo-Celtic.
>
> More likely I've identified playful poetic
> licence. Though Old Irish itself got pretty
> agglutinative for a while, with infixed pronouns
> and such.

I would like to know more about agglutination in Old
Irish.  Could someone point me to more information, either
hard copy or on the web?

Thanks,
Ph. D.