diff --git a/ch06.asciidoc b/ch06.asciidoc
index c80970ee..00d140c3 100644
--- a/ch06.asciidoc
+++ b/ch06.asciidoc
@@ -282,7 +282,7 @@ Hints:
 [[tx_fees]]
 ==== Transaction Fees
 
-Most transactions include transaction fees, which compensate the bitcoin miners for securing the network. Fees also serve as a security mechanism themselves, by making it economically infeasible for attackers to flood the network with transactions. Mining and the fees and rewards collected by miners are discussed in more detail in <<bitcoin_network_ch08>>.
+((("transactions", "outputs and inputs", "transaction fees")))((("transaction fees")))Most transactions include transaction fees, which compensate the bitcoin miners for securing the network. Fees also serve as a security mechanism themselves, by making it economically infeasible for attackers to flood the network with transactions. Mining and the fees and rewards collected by miners are discussed in more detail in <<bitcoin_network_ch08>>.
 
 This section examines how transaction fees are included in a typical transaction. Most wallets calculate and include transaction fees automatically. However, if you are constructing transactions programmatically, or using a command-line interface, you must manually account for and include these fees.