Edited ch04_keys.adoc with Atlas code editor

ch04_keys.adoc

@@ -1815,7 +1815,7 @@ the future unless the preceding problems ((("public key cryptography", "vanity a
 [[paper_wallets]]
 ==== Paper Wallets
 
-Paper wallets are private keys printed on paper.
+Paper wallets((("public key cryptography", "paper wallets", id="pub-key-paper")))((("paper wallets", id="paper-wallet")))((("wallets", "paper", id="wallet-paper"))) are private keys printed on paper.
 Often the paper wallet also includes the corresponding Bitcoin address
 for convenience, but this is not necessary because it can be derived
 from the private key.
@@ -1855,5 +1855,5 @@ spenders to identify the wallets that should receive their payments.
 But when it's actually your wallet receiving the payments, you're going
 to want the assurance that you'll still have access to that money even
 if something happens to your wallet data.  In the next chapter, we'll
-look at how Bitcoin wallets are designed to protect their funds from a
+look at how Bitcoin wallets are designed to protect their funds ((("public key cryptography", "paper wallets", startref="pub-key-paper")))((("paper wallets", startref="paper-wallet")))((("wallets", "paper", startref="wallet-paper")))from a
 variety of threats.