Minor edits from David.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

mixin.tex

@@ -60,7 +60,7 @@ \section{Pictorial interpretation}
 \begin{definition}[Well-formedness of component shapes] \normalfont{}
 A shape $\lctxpair{\provs}{\reqs}$ is \emph{well-formed} if:
 \begin{enumerate}
-\item It does not provide a module variables
+\item It does not provide module variables
 (there is no $m$ such that $\hv{m} \in \textsf{range}(\provs)$),
 e.g., $\lctxpair{\{\prov{B}{\hv{A}}\}}{\hv{A}}$ is ill-formed,
 \item It does not require what it provides (no $m$

overview.tex

@@ -205,6 +205,9 @@ \section{Mixin linking to a \unit{}}
     renaming $r$.  $P$ is an \uid{}; a \cid{} augmented with a
     \emph{module substitution} $S ::= \overline{\subst{m}{M}}$
     specifying how every requirement of the component is instantiated.
+    A \uid{} need not be fully instantiated: we can also leave some
+    requirements uninstantiated by recording a \emph{module hole}
+    ($\hv{m}$) in the module substitution.
     (Compare to the \texttt{mixin} in a \ccomp{}, which only gives a \cid{}).
     \item \UsynMod{m}{\Uhsbody} indicates that this component defines
     a module named $m$ with Haskell source code $\Uhsbody$.

tour.tex

@@ -640,6 +640,18 @@ \section{Refining types in signatures}
 Previously, this would not have been possible, because the
 abstract type \verb|Chr| was considered distinct from \verb|Char|.
 
+Similarly, you could refine an abstract data type with a concrete
+data declaration, like below:
+
+\begin{lstlisting}
+    signature Str where
+        data Chr = Zero | One
+\end{lstlisting}
+
+\noindent
+This \verb|Chr| doesn't define a data type per se, but it can only
+be implemented by a data type with exactly the same constructors.
+
 \section{Reusing and thinning signatures}
 
 For applications more complex than a regular expression matcher, the set
@@ -657,7 +669,6 @@ \section{Reusing and thinning signatures}
     version: 1.0
     library
         signatures: Str
-        build-depends: base
 \end{lstlisting}
 
 \noindent