Merge pull request AllenDowney#54 from jorge-e/patch-7

AllenDowney · web-flow · commit 4d3564e659e3 · 2019-12-30T09:00:53.000-05:00
Fixes
diff --git a/book/book.tex b/book/book.tex
@@ -8472,7 +8472,7 @@ \section{Exercises}
 
 \begin{exercise}
 \index{append method}
-\index{method append}
+\index{method!append}
 \index{list!concatenation}
 \index{concatenation!list}
 
