TODO: Does not currently need to support options.access, options.encode, auto-linking and COinS (as in external_link_id), but may be needed in the future for :m:Interwiki_map custom-prefixes like :arxiv:, :bibcode:, :DOI:, :hdl:, :ISSN:, JSTOR:, :Openlibrary:, :PMID:, :RFC:.