diff --git a/README.md b/README.md
index a32af01b..46bdac30 100644
--- a/README.md
+++ b/README.md
@@ -21,7 +21,7 @@ If you use NPM, `npm install d3`. Otherwise, download the [latest release](https
 
 Array manipulation, ordering, searching, summarizing, etc.
 
-### [Statistics](https://github.com/d3/d3-array#statistics)
+#### [Statistics](https://github.com/d3/d3-array#statistics)
 
 Methods for computing basic summary statistics.
 
@@ -35,7 +35,7 @@ Methods for computing basic summary statistics.
 * [d3.variance](https://github.com/d3/d3-array#variance) - compute the variance of an array of numbers.
 * [d3.deviation](https://github.com/d3/d3-array#deviation) - compute the standard deviation of an array of numbers.
 
-### [Search](https://github.com/d3/d3-array#search)
+#### [Search](https://github.com/d3/d3-array#search)
 
 Methods for searching arrays for a specific element.
 
@@ -47,7 +47,7 @@ Methods for searching arrays for a specific element.
 * [d3.ascending](https://github.com/d3/d3-array#ascending) - compute the natural order of two values.
 * [d3.descending](https://github.com/d3/d3-array#descending) - compute the natural order of two values.
 
-### [Transformations](https://github.com/d3/d3-array#transformations)
+#### [Transformations](https://github.com/d3/d3-array#transformations)
 
 Methods for transforming arrays and for generating new arrays.
 
@@ -61,7 +61,7 @@ Methods for transforming arrays and for generating new arrays.
 * [d3.transpose](https://github.com/d3/d3-array#transpose) - transpose an array of arrays.
 * [d3.zip](https://github.com/d3/d3-array#zip) - transpose a variable number of arrays.
 
-### [Objects](https://github.com/d3/d3-array#objects)
+#### [Objects](https://github.com/d3/d3-array#objects)
 
 Methods for converting associative arrays (objects) to arrays.
 
@@ -69,7 +69,7 @@ Methods for converting associative arrays (objects) to arrays.
 * [d3.values](https://github.com/d3/d3-array#values) - list the values of an associated array.
 * [d3.entries](https://github.com/d3/d3-array#entries) - list the key-value entries of an associative array.
 
-### [Maps](https://github.com/d3/d3-array#maps)
+#### [Maps](https://github.com/d3/d3-array#maps)
 
 Like ES6 Map, but with string keys and a few other differences.
 
@@ -86,7 +86,7 @@ Like ES6 Map, but with string keys and a few other differences.
 * [*map*.empty](https://github.com/d3/d3-array#map_empty) - returns false if the map has at least one entry.
 * [*map*.size](https://github.com/d3/d3-array#map_size) - returns the number of entries in the map.
 
-### [Sets](https://github.com/d3/d3-array#sets)
+#### [Sets](https://github.com/d3/d3-array#sets)
 
 Like ES6 Set, but with string keys and a few other differences.
 
@@ -100,7 +100,7 @@ Like ES6 Set, but with string keys and a few other differences.
 * [*set*.empty](https://github.com/d3/d3-array#set_empty) - returns true if the set has at least one value.
 * [*set*.size](https://github.com/d3/d3-array#set_size) - returns the number of values in the set.
 
-### [Nests](https://github.com/d3/d3-array#nests)
+#### [Nests](https://github.com/d3/d3-array#nests)
 
 Group data into arbitrary hierarchies.
 
@@ -113,7 +113,7 @@ Group data into arbitrary hierarchies.
 * [*nest*.object](https://github.com/d3/d3-array#nest_object) - generate the nest, returning an associative array.
 * [*nest*.entries](https://github.com/d3/d3-array#nest_entries) - generate the nest, returning an array of key-values tuples.
 
-### [Histograms](https://github.com/d3/d3-array#histograms)
+#### [Histograms](https://github.com/d3/d3-array#histograms)
 
 Bin discrete samples into continuous, non-overlapping intervals.