diff --git a/ch04_keys.adoc b/ch04_keys.adoc
index 1d69f2f3..c911a961 100644
--- a/ch04_keys.adoc
+++ b/ch04_keys.adoc
@@ -1771,7 +1771,7 @@ GPUs.
 Vanity searches on GPU systems are many orders of magnitude
 faster than on a general-purpose CPU.
 
-Another way to find a vanity address is to outsource the work to a pool
+Another((("vanity pools"))) way to find a vanity address is to outsource the work to a pool
 of vanity miners. A https://oreil.ly/99K81[vanity pool] is a service that
 allows those with fast hardware to earn bitcoin searching for vanity
 addresses for others. For a fee, Eugenia can outsource the search for a