diff --git a/ch04_keys.adoc b/ch04_keys.adoc
index 0f9be64f..57267879 100644
--- a/ch04_keys.adoc
+++ b/ch04_keys.adoc
@@ -382,7 +382,7 @@ image::images/mbc3_0404.png["ecc_illustrated"]
 
 === Output and Input Scripts
 
-Although the illustration from the original Bitcoin paper, <<pay-to-pure-pubkey>>,
+Although((("public key cryptography", "input/output scripts", id="pub-key-input-output")))((("input scripts", id="input-script")))((("output scripts", id="output-script")))((("scripts", "input/output", id="script-input-output"))) the illustration from the original Bitcoin paper, <<pay-to-pure-pubkey>>,
 shows public keys (pubkeys) and signatures (sigs) being used directly,
 the first version of Bitcoin instead had payments sent to a field called
 _output script_ and had spends of those bitcoins authorized by a field called _input script_.
@@ -394,7 +394,7 @@ corresponding signatures be placed in the spending input script.
 Later, in <<tx_script>>, we'll learn about scripts in detail.  For now,
 all we need to understand is that bitcoins are received to an
 output script that acts like a public key, and bitcoin spending is
-authorized by an input script that acts like a signature.
+authorized by an input script that acts like a ((("public key cryptography", "input/output scripts", startref="pub-key-input-output")))((("input scripts", startref="input-script")))((("output scripts", startref="output-script")))((("scripts", "input/output", startref="script-input-output")))signature.
 
 [[p2pk]]
 === IP Addresses: The Original Address for Bitcoin (P2PK)