searching a ldap tree

[fnijen <fnijen@bos.nl>]

Hi, ldap guru's,

I've a fairly simple ldap tree:

a: top=whatever
b: oc=country
c: oc=organisation
d: oc=person

When I do a search on companyname with searchfilter (companyname=bos.nl), the
server returns all entry's found, no matter under which country they resort.
But when I specify the countrycode. Like 
(&(|(countrycode=nl)(countrycode=uk))(companyname=bos.nl))
the server does not return anything, and it should return two entry's since 
the company has an office in uk and nl. (I confirmed that the entry's exist).
The countrycode is an attribute of oc=country, the companyname an attribute 
of oc=companyname.

I think I missed some serious information about the use of searchfilters 
and traversing an ldap tree structure.
Are there some papers on the net about this topic? The rfc isn't of much help.

Can anyone help me out here?

Thanks

Frank