Order by in stored functions

Hello

I tried to create the following function

CREATE Function pGetMenu ( int ) returns setof varchar As '   SELECT IdMenuShow || IdWebPage   FROM   Menu   WHERE
IdMenu= $1    ORDER BY IdSort ; ' language 'SQL' ;
 

I've got the following error message:

ERROR:  function declared to return varchar returns multiple values in final retrieve

If O just remove the ORDER BY clause als works well so I guess that the
ORDER BY has to be replaced by somethjing other.  Could somebody
enlighten me how to do the ordering in a stored procedure?

Kind regards
         Andreas.