diff --git a/appb_errata.adoc b/appb_errata.adoc
index ac996048..b1c16ed1 100644
--- a/appb_errata.adoc
+++ b/appb_errata.adoc
@@ -107,7 +107,7 @@ chain-like; it’s more accurately described as a directed acyclic ((("transacti
 === Proof of Work
 
 ____
-"we implement the proof-of-work by incrementing a nonce in the block
+"we implement ((("Proof-of-Work algorithm", "errata in Bitcoin whitepaper", id="proof-errata")))the proof-of-work by incrementing a nonce in the block
 until a value is found that gives the block’s hash the required zero
 bits."
 ____
@@ -148,12 +148,12 @@ Further, the average implemented in Bitcoin targets an average number of
 blocks per two weeks (not per hour as might be implied by the text).
 Other implemented rules may further slow adjustments, such as a rule
 that the adjustment cannot increase block production speed by more than
-300% per period, nor slow it by more than 75%.
+300% per period, nor slow it by more ((("Proof-of-Work algorithm", "errata in Bitcoin whitepaper", startref="proof-errata")))than 75%.
 
 === Reclaiming Disk Space
 
 ____
-"Once the latest transaction in a coin is buried under enough blocks, the
+"Once the((("disk space", "reclaiming")))((("reclaiming", "disk space"))) latest transaction in a coin is buried under enough blocks, the
 spent transactions before it can be discarded to save disk space"
 ____