Those more directly involved may wish to correct my impression, but I believe that the token _citation.journal_coden_PDB should more properly be called _citation.journal_coden_CSD or _citation.journal_coden_CSD_PDB. For simplicity, I would suggest defining _citation.journal_coden_CSD and making _citation.journal_coden_PDB an alias of _citation.journal_coden_CSD. I may be wrong, but I believe that this would carry reasonably accurate connotations about the history and use of this coden. If my recollection is correct, the coden series involved was started by CCDC and has been jointly extended as required by both CCDC and BNL.