---
title: "References cited by a DOI"
method: GET
path: "/api/v1/research/crossref/references/{doi}"
tags: ["Research"]
---

# References cited by a DOI

`GET /api/v1/research/crossref/references/{doi}`

Extract the deposited reference list (outbound citations) for a given DOI. Returned from the `reference[]` array of the work record - present only when the publisher has deposited references. No extra upstream call is made (the work envelope is fetched once, reshaped). Data licensed CC0 by Crossref.

## Path parameters

- `doi` string, required — DOI of the source work (e.g. `10.1038/nature12373`). Forward slashes are preserved.

## Response `200`

Reference list deposited by the publisher, with the source DOI's `indexed_date_time`.

- EnvelopeCrossrefReferencesPayload
  - `data` CrossrefReferencesPayload, required — Response payload for `/api/v1/research/crossref/references/{doi}`.
    - `doi` string, required — DOI of the source work whose references are returned.
    - `reference_count` integer, nullable — Number of references deposited by the publisher (source of the list below).
    - `references` CrossrefReference[], required — Deposited reference list (outbound citations) as filed by the publisher.
      - `key` string, nullable — Publisher-assigned reference key (e.g. `ref_1`).
      - `DOI` string, nullable — DOI of the cited work when deposited.
      - `doi-asserted-by` string, nullable — Entity that asserted the DOI mapping (`publisher` or `crossref`).
      - `unstructured` string, nullable — Free-text citation when no structured DOI or metadata is available.
      - `article-title` string, nullable — Title of the cited article when structured.
      - `journal-title` string, nullable — Journal title for the cited article when structured.
      - `volume-title` string, nullable — Volume or book title when citing a chapter or edited volume.
      - `author` string, nullable — Author surname string for the cited work.
      - `year` string, nullable — Publication year string for the cited work.
      - `volume` string, nullable — Volume number of the cited work.
      - `issue` string, nullable — Issue number of the cited work.
      - `first-page` string, nullable — First page of the cited work.
      - `ISSN` string, nullable — ISSN of the cited journal.
      - `isbn-type` string, nullable — ISBN type (e.g. `print`, `electronic`).
      - `component` string, nullable — Component identifier (used when citing book chapters or data).
    - `indexed_date_time` string, nullable — ISO 8601 timestamp of Crossref's last re-index of the source work.
  - `meta` SugraMeta, required — Metadata attached to every /api/v1/* response envelope.
    - `endpoint` string, required — Requested endpoint path.
    - `data_time` string, required — ISO 8601 UTC timestamp of the source data, not of the request.
    - `response_time` string, required — ISO 8601 UTC timestamp when this response was produced.
    - `provider` string, required — API name and version.
    - `source` string, nullable — Identifier of the primary upstream source used for this response.
    - `attribution` string, nullable — Human-readable attribution mandated by an upstream source (e.g. a securities regulator or self-regulatory organization). Present only on responses whose source requires the owner and source to be clearly identified. Do not remove or alter it when using the response.
    - `fallback_used` boolean, nullable — True when the primary source failed and a fallback produced the data.
    - `fallback_chain` string[], nullable — Ordered list of sources attempted, in the order they were tried.
    - `cached` boolean, nullable — True when this response was served from the internal cache.
    - `stale` boolean, nullable — True when the cached response was returned after the upstream rate-limited or errored. Clients can use this to detect degraded data.

## Other responses

- `401` — Missing or invalid `x-api-key` header.
- `422` — Validation Error
- `429` — Daily rate limit exceeded. Check `X-RateLimit-Reset` for the next window.
- `503` — Upstream source is temporarily unavailable. Retry after a short delay.

---

[API](https://skmtc.net/sugra/apis/sugra-api.md) · [All operations](https://skmtc.net/sugra/apis/sugra-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/sugra/sugra-api/versions/4e2740743eb4/schema)