diff --git a/ch04_keys.adoc b/ch04_keys.adoc
index 57267879..9563f6eb 100644
--- a/ch04_keys.adoc
+++ b/ch04_keys.adoc
@@ -399,7 +399,7 @@ authorized by an input script that acts like a ((("public key cryptography", "in
 [[p2pk]]
 === IP Addresses: The Original Address for Bitcoin (P2PK)
 
-We've established that Alice can pay Bob by assigning some of her
+We've ((("public key cryptography", "IP address payments and", id="pub-key-ipaddress")))((("IP addresses", "for Bitcoin payments", secondary-sortas="Bitcoin payments", id="ipaddress-payment")))((("payments", "via IP addresses", id="payment-ipaddress")))((("P2PK (pay to public key)", id="p2pk")))established that Alice can pay Bob by assigning some of her
 bitcoins to one of Bob's public keys.  But how does Alice get one of
 Bob's public keys?  Bob could just give her a copy, but let's look again
 at the public key we worked with in <<public_key_derivation>>.  Notice
@@ -474,7 +474,7 @@ to see the benefits when we look at the following section.
 
 This type of output is known today as _pay to public key_, or _P2PK_ for
 short.  It was never widely used for payments, and no widely used
-program has supported IP address payments for almost a decade.
+program has supported IP address payments for almost((("public key cryptography", "IP address payments and", startref="pub-key-ipaddress")))((("IP addresses", "for Bitcoin payments", secondary-sortas="Bitcoin payments", startref="ipaddress-payment")))((("payments", "via IP addresses", startref="payment-ipaddress")))((("P2PK (pay to public key)", startref="p2pk"))) a decade.
 
 [[addresses_for_p2pkh]]
 === Legacy Addresses for P2PKH