[Zope] How do I get the owner of a document?

Hi, may be I am just to dumb or something like that, but Zope has to now who is the owner of a certain document. This is for sure, but how can I get the owner of a document from DTML or an external method? I read through the sources and maybe I am just to dumb or so to find it, but I can't find any manage_* call, that tells me how to do this? I have to write a small DTML method, that finds all documents, that are located in a givben hierachie which are owned by a certain user. Bye and many thanks, OLiver P.S.: Don't frustrated that I ask these things again and again, but now I have to deal with things in Zope, that I haven't dealt with before. ;-))))