diff --git a/protocol/protocol.tex b/protocol/protocol.tex
index dc2e8ce4..49341ce1 100644
--- a/protocol/protocol.tex
+++ b/protocol/protocol.tex
@@ -269,6 +269,7 @@
 \newcommand{\lemmaref}[1]{\raisebox{0ex}{\hyperref[#1]{Lemma \ref*{#1}\vphantom{,}}} on p.\,\pageref*{#1}}
 \newcommand{\footnoteref}[1]{\hairspace\raisebox{0ex}{\cref{#1}}}
 \newcommand{\snarkref}[2]{\raisebox{0ex}{\hyperref[#2]{\linkstrut\smash{\textbf{#1}}}}}
+\newcommand{\historyref}[1]{\raisebox{0ex}{\hyperref[#1]{\linkstrut\smash{v#1}}}}
 
 \newcommand{\callout}[2]{\vspace{1ex plus 2pt minus 2pt}#1\textbf{#2}\hspace{1em}}
 \newcommand{\historyentry}[2]{\introlist\extralabel{#1}{\headingandlabel{\callout{}{#1}{#2}}{\##1}}}
@@ -13383,7 +13384,7 @@ The \targetThreshold for a given \blockHeight $\BlockHeight$ is then calculated
         in the definition of $\MedianTime$ during the first $\PoWAveragingWindow - 1$ \blocks of
         the \blockChain), the element that begins the second half of the sequence is taken.
         This corresponds to the \zcashd implementation, but was not specified correctly in versions
-        of this specification prior to 2019.0-beta-40.
+        of this specification prior to \historyref{2019.0.0}.
 \end{pnotes}
 
 On \Testnet from \blockHeight $299188$ onward, the difficulty adjustment algorithm
@@ -14495,6 +14496,13 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
 \lsection{Change History}{changehistory}
 
 
+\historyentry{2021.2.15}{}
+\begin{itemize}
+    \item Fix a reference to nonexistent version 2019.0-beta-40 of this specification
+          (in \crossref{diffadjustment}) that should be \historyref{2019.0.0}.
+\end{itemize}
+
+
 \historyentry{2021.2.14}{2021-08-12}
 \begin{itemize}
 \nufive{
@@ -14956,8 +14964,8 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
           $\PoseidonHash$.
 } %nufive
 \sapling{
-    \item The subgroup check added to \crossref{decryptovk} for \Sapling in version 2021.1.17 was
-          applied to the wrong variable ($\DiversifiedTransmitBase$, when it should have been
+    \item The subgroup check added to \crossref{decryptovk} for \Sapling in \historyref{2021.1.17}
+          was applied to the wrong variable ($\DiversifiedTransmitBase$, when it should have been
           $\DiversifiedTransmitPublic$), despite being described correctly in the Change History
           entry below.
 } %sapling
@@ -15138,8 +15146,8 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
     \item Acknowledge Jane Lusby and Teor.
     \item Precisely specify the encoding and decoding of \EdSpecific points.
 \sapling{
-    \item Correct an error introduced in 2020.1.8; ``$-\ZeroJ$'' was incorrectly used when
-          the point $(0, -1)$ on \Jubjub was meant.
+    \item Correct an error introduced in \historyref{2020.1.8}; ``$-\ZeroJ$'' was incorrectly
+          used when the point $(0, -1)$ on \Jubjub was meant.
     \item Precisely specify the conversion from a bit sequence in $\abstJ$.
 } %sapling
 \end{itemize}
@@ -15526,7 +15534,7 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
     \item Correct the input to $\RedDSAHashToScalar$ used to derive the nonce $r$ in
           $\RedDSASign{}$, from $T \bconcat M$ to $T \bconcat \vkBytes{} \bconcat M$.
           This matches the sapling-crypto implementation; the specification of this
-          input was unintentionally changed in version 2018.0-beta-20.
+          input was unintentionally changed in \historyref{2018.0-beta-20}.
     \item Clarify the description of the Merkle path check in \crossref{cctmerklepath}.
 } %sapling
 \end{itemize}