diff --git a/ch06.asciidoc b/ch06.asciidoc
index 8b188547..42dd119b 100644
--- a/ch06.asciidoc
+++ b/ch06.asciidoc
@@ -124,7 +124,7 @@ The topic of locking and unlocking UTXO will be discussed later, in <<tx_lock_un
 
 ===== Transaction serialization&#x2014;outputs
 
-When transactions are transmitted over the network or exchanged between applications, they are _serialized_. Serialization is the process of converting the internal representation of a data structure into a format that can be transmitted one byte at a time, also known as a byte-stream. Serialization is most commonly used for encoding data structures for transmission over a network or for storage in a file. The serialization format of a transaction output is shown in <<tx_out_structure>>.
+((("transactions", "outputs and inputs", "structure of")))((("outputs and inputs", "structure of")))When transactions are transmitted over the network or exchanged between applications, they are _serialized_. Serialization is the process of converting the internal representation of a data structure into a format that can be transmitted one byte at a time, also known as a byte-stream. Serialization is most commonly used for encoding data structures for transmission over a network or for storage in a file. The serialization format of a transaction output is shown in <<tx_out_structure>>.
 
 [[tx_out_structure]]
 .Transaction output serialization