Add ref to Bogomolov ineq

tex/setting-and-problems.tex

@@ -110,7 +110,7 @@ $d \in \frac{1}{\lcm(m,2)}\ZZ$.
 	(otherwise the destabilising subobject would also destabilise $F$).
 	Similarly $G$ must also be semistable too.
 	$E$ and $G$ being semistable implies they also satisfy the Bogomolov
-	inequalities:
+	inequalities (Theorem \ref{lem:bogomolov-inequality}):
 	% TODO ref Bogomolov inequalities for tilt stability
 	$\Delta(E), \Delta(G) \geq 0$.
 	Expressing this in terms of Chern characters for $E$ and $F$ gives: