Since it's something from an archive (record kept for the functioning of an institution, presumably the one organizing the conference), an acceptable form according to my handbook on the subject would be:

Agenda of [conference name/location and date], [name of archive], [section name], inv. nr. [whatever number it was given].

But the format isn't necessarily important in such cases, as long as it's made clear where the reader can find the relevant document and verify the citation.