Add research field mapping for OAI-PMH interface at HZB
Add / update research field mapping for OAI-PMH interface.
Specifically for HZB, this information is encrypted in <setSpec></setSpec>
in the xml header.
Example record: https://www.helmholtz-berlin.de/pubbin/oai?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai:helmholtz.HZB:107838 (for the record: list all available sets: https://www.helmholtz-berlin.de/pubbin/oai?verb=ListSets)
Please see the suggested mapping in the dictionary commented below.