# Source registry — the authorities the skills cite

This registry holds **authority citations**: the methodological sources that ground a decision. They answer *why was this operation legitimate or blocked*.

They are not the same thing as **data citations**, which identify which observations were used, from whom, pulled when. Data citations are built by `citing-official-statistics` from the unit set. A decision record needs both, and one never substitutes for the other — citing the IMF Quarterly National Accounts Manual explains why chain-linked volumes cannot be summed, but says nothing about which series you actually used.

Cite from this table verbatim: authority, locator, link. Give the user authority + locator + link, never the registry id. Where both a DOI and a provider URL exist, prefer the DOI.

Instance-level metadata — a specific dataflow's ESMS/SIMS page or methodology note — is **not** in this registry. It is taken from what the Aard MCP server returns for the dataflow and carried on the data unit as `metadata_url`. Never construct one. Where none is returned, set `metadata_unavailable=true`; reserve `metadata_absent=true` for positive evidence that the producer publishes none. The two are not interchangeable, and only the latter can stand in for an instance citation — see `references/units-and-tiers.md`.

| id | Authority | Locator | Link | Grounds |
|---|---|---|---|---|
| `imf-qna` | IMF, Quarterly National Accounts Manual (2017 ed.) | Ch. 8, Price and Volume Measures | https://www.imf.org/en/Publications/Manuals-Guides/Issues/2017/06/09/Quarterly-National-Accounts-Manual-2017-Edition-44776 | Guard rules a, g — chain-linked non-additivity; nominal/real discipline |
| `abs-asna` | ABS, Australian System of National Accounts: Concepts, Sources and Methods, Ed. 8 | section 6.34 | https://www.abs.gov.au/statistics/detailed-methodology-information/concepts-sources-methods/australian-system-national-accounts-concepts-sources-and-methods/latest-release | Guard rule a — contributions to growth are additive; chain volume components are not |
| `estat-nama10` | Eurostat, nama_10 ESMS reference metadata | annexes on chain-linking | https://ec.europa.eu/eurostat/cache/metadata/en/nama10_esms.htm | Guard rule a — chain-linked components do not sum to the aggregate |
| `ppp-faq` | Eurostat–OECD, FAQ on Purchasing Power Parities | sections on use of PPPs vs exchange rates | https://ec.europa.eu/eurostat/web/purchasing-power-parities | Guard rules c, d — growth rates and own-currency ratios need neither PPPs nor exchange rates; PPPs for spatial volume comparison only; AIC preferred for material well-being |
| `estat-se-ppp` | Eurostat Statistics Explained, PPPs and GDP per capita | ranking caveat | https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Purchasing_power_parities_and_GDP_per_capita_-_preliminary_estimate | Guard rule d — volume indices not intended to rank countries strictly |
| `simpson-1951` | Simpson, The Interpretation of Interaction in Contingency Tables, JRSS B 13(2) | pp. 238–241 | https://doi.org/10.1111/j.2517-6161.1951.tb00088.x | Guard rule b — aggregation-order reversal |
| `oecd-jrc` | OECD/EC-JRC, Handbook on Constructing Composite Indicators (2008) | ten-step methodology; step 7 mandatory | https://doi.org/10.1787/9789264043466-en | Guard rule k — composite construction discipline |
| `fs-1969` | Fellegi & Sunter, A Theory for Record Linkage, JASA 64(328) | three-region decision rule, pp. 1183–1210 | https://doi.org/10.1080/01621459.1969.10501049 | Tier 4 — the clerical-review region; why escalation beats silent computation |
| `horvitz-1999` | Horvitz, Principles of Mixed-Initiative User Interfaces, CHI '99 | pp. 159–166 | https://doi.org/10.1145/302979.303030 | Tier-4 escalation format — dialogue resolving key uncertainty; actionable choice, not disclaimer |
| `sdmx-glossary` | SDMX Glossary / Metadata Common Vocabulary | coherence; comparability | https://sdmx.org/guidelines/ | Tier semantics — the coherence vs comparability distinction |
| `force11-jddcp` | Data Citation Synthesis Group, Joint Declaration of Data Citation Principles (Martone ed.), FORCE11, 2014 | principles 3 (Evidence), 7 (Specificity and Verifiability) | https://doi.org/10.25490/a97f-egyk | Why every surfaced observation needs a resolvable identifier — validation leg 4 |
| `rda-dynamic` | RDA Working Group on Data Citation, Recommendations | R1–R8, versioning / timestamping / query identification | https://www.rd-alliance.org/group/data-citation-wg/outcomes/data-citation-recommendation.html | Citing a query rather than a dataset; extraction timestamps and result checksums |

**Maintenance.** If a link rots, replace it with the DOI or the provider's current canonical page; never delete a row a shipped skill cites. DOIs here are permanent; the IMF, ABS and Eurostat landing pages are current canonical pages and should be link-checked periodically.

**Known wording caveat.** The 2012 PPP FAQ PDF does not contain the literal phrases "statistical constructs" or "near neighbours". Guard rule d therefore cites the Eurostat *Statistics Explained* wording (`estat-se-ppp`), which is exact and linkable.