diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4acdfb6..f877f88 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## 0.5.0 (unreleased)
 
+- Added HNSW index type
 - Added support for parallel index builds
 - Added `l1_distance` function
 - Added element-wise multiplication for vectors
diff --git a/README.md b/README.md
index 550a2ef..15a11a7 100644
--- a/README.md
+++ b/README.md
@@ -562,6 +562,7 @@ Thanks to:
 - [Using the Triangle Inequality to Accelerate k-means](https://www.aaai.org/Papers/ICML/2003/ICML03-022.pdf)
 - [k-means++: The Advantage of Careful Seeding](https://theory.stanford.edu/~sergei/papers/kMeansPP-soda.pdf)
 - [Concept Decompositions for Large Sparse Text Data using Clustering](https://www.cs.utexas.edu/users/inderjit/public_papers/concept_mlj.pdf)
+- [Efficient and Robust Approximate Nearest Neighbor Search using Hierarchical Navigable Small World Graphs](https://arxiv.org/ftp/arxiv/papers/1603/1603.09320.pdf)
 
 ## History