Retrograde edits

src/Advanced/De Bruijn/parts/3 line.tex

@@ -49,6 +49,7 @@ Have an instructor check your solution.
 				(0) edge (2)
 				(2) edge (3)
 				(2) edge[bend left] (4)
+				(4) edge[bend left] (2)
 				(3) edge (1)
 				(4) edge (3)
 				(4) edge[loop right] (4)

src/Advanced/De Bruijn/parts/4 sturmian.tex

@@ -375,7 +375,7 @@ Construct a minimal Sturmain word of order 5.
 
 
 \problem{}
-Show that the words we get by \ref{sturmanthm} are minimal Sturmain words. \par
+Argue that the words we get by \ref{sturmanthm} are minimal Sturmain words. \par
 That is, the word $w$ has length $2n$ and $\mathcal{S}_m(w) = m + 1$ for all $m \leq n$.
 
 \begin{solution}

src/Advanced/Retrograde Analysis/parts/02 easy.tex

@@ -252,7 +252,7 @@ It is Black's move. Can Black castle? \par
 \difficulty{2}{5}
 
 Neither Black nor White captured a piece on their last move. \par
-It is Black's move. Show that he cannot castle? \par
+It is Black's move. Can he castle? \par
 \hint{What was White's last move? Check the cases.}
 
 \manyboards{
@@ -348,7 +348,7 @@ It is White's move. What was the previous move?
 	Bc8,
 	pg6,
 	Pg5,kh5,
-	Pd4,qg4,bh4,
+	Pd4,Qg4,Bh4,
 	pd3,
 	Pd2,Be2,Bg2,
 	Nc1,rd1,Ne1,Kf1,Qg1,Rh1