diff --git a/ch11_blockchain.adoc b/ch11_blockchain.adoc
index 9dfae935..c9d699af 100644
--- a/ch11_blockchain.adoc
+++ b/ch11_blockchain.adoc
@@ -524,7 +524,7 @@ largest possible Bitcoin block.
 
 === Merkle Trees and Lightweight Clients
 
-Merkle trees are used extensively by lightweight clients. Lightweight clients don't
+Merkle trees are ((("Bitcoin network", "lightweight clients", "merkle trees and")))((("lightweight clients", "merkle trees and")))used extensively by lightweight clients. Lightweight clients don't
 have all transactions and do not download full blocks, just block
 headers. In order to verify that a transaction is included in a block,
 without having to download all the transactions in the block, they use