Index: detour/2_topo.html
===================================================================
--- detour/2_topo.html	(revision 889)
+++ detour/2_topo.html	(revision 890)
@@ -4,6 +4,10 @@
 <h1> Topo-geometric detour router </h1>
 
 <h2> 2. Detour search </h2>
+<p>
+This chapter focuses on the topological (high) level of the router and assumes
+the geometrical (low) level is available and can calculate the geometry of
+a detour of a trace object and a network.
 
 <h3> 2.1. Board state </h3>
 <p>
Index: detour/index.html
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--- detour/index.html	(revision 889)
+++ detour/index.html	(revision 890)
@@ -7,5 +7,5 @@
 <ul>
 	<li> 1. <a href="1_intro.html">Introduction</a>
 	<li> 2. <a href="2_topo.html">Detour search</a> (the topological aspect)
-	<li> 3. Hull path (geometric aspect)
+	<li> 3. <a href="3_geo.html">Convex hull path</a> (geometric aspect)
 </ul>