Index-aligned with authors (same length when present); None per-author where the source didn't carry one. crossref/openalex + import set it.
authors
None
Backend that produced this record; stored as PAPER_META.PROVIDER.
Namespaced ID, e.g. "arxiv:2204.12985", "openalex:W31...", "local:{hash}".
Defaults to 1 for non-arxiv sources.
Index-aligned with
authors(same length when present);Noneper-author where the source didn't carry one. crossref/openalex + import set it.