diff --git a/ch04.asciidoc b/ch04.asciidoc
index 71d9aef5..c2a7dc70 100644
--- a/ch04.asciidoc
+++ b/ch04.asciidoc
@@ -1,7 +1,7 @@
 [[ch04_keys_addresses]]
 == Keys, Addresses
 
-((("bitcoin", "keys and addresses", id="BCkeys04")))((("cryptography", "defined")))((("cryptography", see="also keys and addresses")))You may have heard that bitcoin is based on _cryptography_, which is a branch of mathematics used extensively in computer security. Cryptography means "secret writing" in Greek, but the science of cryptography encompasses more than just secret writing, which is referred to as encryption. Cryptography can also be used to prove knowledge of a secret without revealing that secret (digital signatures), or prove the authenticity of data (digital fingerprints). These types of cryptographic proofs are the mathematical tools critical to bitcoin and used extensively in bitcoin applications. ((("encryption")))((("encryption", see="also keys and addresses")))Ironically, encryption is not an important part of bitcoin, as its communications and transaction data are not encrypted and do not need to be encrypted to protect the funds. In this chapter we will introduce some of the cryptography used in bitcoin to control ownership of funds, in the form of keys, addresses, and wallets. 
+((("cryptography", "defined")))((("cryptography", see="also keys and addresses")))You may have heard that bitcoin is based on _cryptography_, which is a branch of mathematics used extensively in computer security. Cryptography means "secret writing" in Greek, but the science of cryptography encompasses more than just secret writing, which is referred to as encryption. Cryptography can also be used to prove knowledge of a secret without revealing that secret (digital signatures), or prove the authenticity of data (digital fingerprints). These types of cryptographic proofs are the mathematical tools critical to bitcoin and used extensively in bitcoin applications. ((("encryption")))((("encryption", see="also keys and addresses")))Ironically, encryption is not an important part of bitcoin, as its communications and transaction data are not encrypted and do not need to be encrypted to protect the funds. In this chapter we will introduce some of the cryptography used in bitcoin to control ownership of funds, in the form of keys, addresses, and wallets. 
 
 === Introduction
 
@@ -816,7 +816,7 @@ image::images/mbc2_0410.png[]
 .The bitcoinpaperwallet.com paper wallet with the private key concealed
 image::images/mbc2_0411.png[]
 
-Other designs feature additional copies of the key and address, in the form of detachable stubs similar to ticket stubs, allowing you to store multiple copies to protect against fire, flood, or other natural disasters.((("", startref="BCkeys04")))((("", startref="KAadvanced04")))((("", startref="Wpaper04")))((("", startref="paperw04"))) 
+Other designs feature additional copies of the key and address, in the form of detachable stubs similar to ticket stubs, allowing you to store multiple copies to protect against fire, flood, or other natural disasters.((("", startref="KAadvanced04")))((("", startref="Wpaper04")))((("", startref="paperw04"))) 
 
 [[paper_wallet_spw]]
 .An example of a paper wallet with additional copies of the keys on a backup "stub"