start CHANGELOG for refs work

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diff --git a/CHANGELOG.md b/CHANGELOG.md
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--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,11 @@ See also:
 
 ## Unreleased
 
+### Added
+
+- reference graph views, based on fuzzy reference dataset in `cgraph` and
+  `fatcat-scholar` projects, stored in elasticsearch index
+
 ### Fixed
 
 - viewing deleted release entities no longer result in 500 error
diff --git a/guide/src/SUMMARY.md b/guide/src/SUMMARY.md
index ffc80ac2..c7d12cb0 100644
--- a/guide/src/SUMMARY.md
+++ b/guide/src/SUMMARY.md
@@ -8,6 +8,7 @@
     - [Goals and Related Projects](./goals.md)
     - [Data Model](./data_model.md)
     - [Editing Workflow](./workflow.md)
+    - [Reference Graph](./reference_graph.md)
     - [Sources of Metadata](./sources.md)
     - [Implementation and Infrastructure](./implementation.md)
     - [Roadmap](./roadmap.md)
@@ -21,6 +22,7 @@
     - [Release](./entity_release.md)
     - [Work](./entity_work.md)
 - [Public API](./http_api.md)
+    - [Search API](./search_api.md)
     - [Bulk Exports](./bulk_exports.md)
     - [Cookbook](./cookbook.md)
 - [Contributing](./contributing.md)
diff --git a/guide/src/reference_graph.md b/guide/src/reference_graph.md
new file mode 100644
index 00000000..3b773150
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+++ b/guide/src/reference_graph.md
@@ -0,0 +1,9 @@
+
+# Reference Graph
+
+As a new feature, fuzzy-matched references are available on an "inbound" and
+"outbound" basis in the web interface.
+
+The backend reference graph is available via the [Search API](./search_api.md)
+under the `fatcat_ref` index.
+
diff --git a/guide/src/search_api.md b/guide/src/search_api.md
new file mode 100644
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+++ b/guide/src/search_api.md
@@ -0,0 +1,29 @@
+
+# Search API
+
+The Elasticsearch indices used to power metadata search, statistics, and graphs
+on the fatcat web interface are exposed publicly at
+`https://search.fatcat.wiki`. Third parties can make queries using the
+Elasticsearch API, which is well documented online and has client libraries in
+many programming languages.
+
+A thin proxy (`es-public-proxy`) filters requests to avoid expensive queries
+which could cause problems for search queries on the web interface, but most of
+the Elasticsearch API is supported, including powerful aggregation queries.
+
+There is a short delay between updates to the fatcat catalog (via the main API)
+and updates to the search index.
+
+Notable indices include:
+
+- `fatcat_release`: release entity metadata
+- `fatcat_container`: container entity metadata
+- `fatcat_ref`: reference graph
+
+Schemas for these indices can be fetched directly from the index (eg,
+`https://search.fatcat.wiki/fatcat_release/_mapping`), and are versioned in the
+fatcat git repository under `fatcat:extra/eleasticsearch/`. They are a
+simplification and transform of the regular entity schemas, and include some
+synthesized fields (such as "preservation status" for releases). Note that the
+search schemas are likely to change over time with less notice and stability
+guarantees than the primary catalog API schema.