DOCBOOK-APPS: Various styles in one document

[Michał Rój <M.Roj@elka.pw.edu.pl>]

Hello men,
I've got the following docbook problem - usually want to produce
documents which should differ in their form in diiferent parts of
my document (e.g. I want to get an article (<article>) which is 2-column,
but the header and abstract should be 1-column ).

Q: Is it possible to apply various stylesheets to
     speciefied parts of my sgml source?

Q: Is it possible to 'link' documents generated from different sources
    and stylesheeets;or (in an exteme form) is it possible to 'link'
    ready documents (e.g. rtf ones) with an output of jade's rtf-backend
    (I espacially mean the tilepages which are required by my university,
    which cannot be produced from a docbook source - the rest of work)

Thanks in advance,
M. Rój