diff --git a/ch06_transactions.adoc b/ch06_transactions.adoc
index 6b798055..a79f148e 100644
--- a/ch06_transactions.adoc
+++ b/ch06_transactions.adoc
@@ -282,7 +282,7 @@ This txid is in Bitcoin's internal byte order for hashes; see
 <<internal_and_display_order>>.
 
 Because transactions may contain multiple outputs, Alice also needs to
-identify which particular output from that transaction to use, called
+identify which particular output from that transaction to use, ((("output indexes")))called
 its _output index_.  Output indexes are 4-byte unsigned
 integers starting from zero.
 
@@ -315,7 +315,7 @@ pieces of information from it:
 - Proof that the previous output exists in the blockchain (or as a known
   unconfirmed transaction) and that no other transaction has spent it.
   One of Bitcoin's consensus rules forbids any output from being spent
-  more than once within a valid blockchain.  This is the rule against
+  more than once within a valid blockchain.  This is the((("double spending")))((("conflicting transactions"))) rule against
   _double spending_: Alice can't use the same previous output to pay
   both Bob and Carol in separate transactions.  Two transactions that each try to spend the
   same previous output are called _conflicting transactions_ because