diff --git a/Exercises.html b/Exercises.html
--- a/Exercises.html
+++ b/Exercises.html
@@ -329,11 +329,11 @@
 <h1 id="programming-environment"
     >Programming Environment</h1
     ><p
-    ><code
+    >Newer <code
       >GHC</code
       > and <code
       >cabal-install</code
-      > are needed.</p
+      > are needed (these are on computers in the lab; Linux is recommended).</p
     ><ol style="list-style-type: decimal;"
     ><li
       >Run the following commands in a terminal:</li
@@ -366,6 +366,10 @@
 	>-maps-exercises</span
 	><span class="Keyword Backquote"
 	>`</span
+	><span class="Normal NormalText"
+	> </span
+	><span class="Keyword Control"
+	>&amp;</span
 	><br
 	 /></code
       ></pre
@@ -720,7 +724,10 @@
       ><span class="Function FunctionDefinition"
 	>revMapWalk ::</span
 	><span class="Normal NormalText"
-	> I i =&gt; Children k -&gt; Set i k -&gt; [Id k] -&gt; [[Id k]]</span
+	> I i =&gt; </span
+	><br
+	 /><span class="Normal NormalText"
+	>    ChildrenFun k -&gt; Set i k -&gt; [Id k] -&gt; [[Id k]]</span
 	><br
 	 /></code
       ></pre
diff --git a/Exercises.pandoc b/Exercises.pandoc
--- a/Exercises.pandoc
+++ b/Exercises.pandoc
@@ -12,14 +12,14 @@
 
 # Programming Environment
 
-`GHC` and `cabal-install` are needed.
+Newer `GHC` and `cabal-install` are needed (these are on computers in the lab; Linux is recommended).
 
 1. Run the following commands in a terminal:
 
 ~~~~~~~~~~~~ {.bash}
 cabal update
 cabal install linear-maps -fcheck
-firefox `linear-maps-exercises`
+firefox `linear-maps-exercises` &
 ~~~~~~~~~~~~
 
 2. Open an editor and save an empty file `Maps.hs` (do not quit).
@@ -172,7 +172,8 @@
 -   Collect the nodes which are present in the set.
 
 ~~~~~~~~ {.haskell}
-revMapWalk :: I i => Children k -> Set i k -> [Id k] -> [[Id k]]
+revMapWalk :: I i => 
+    ChildrenFun k -> Set i k -> [Id k] -> [[Id k]]
 ~~~~~~~~
 
 Help: Use accumulation.
diff --git a/linear-maps.cabal b/linear-maps.cabal
--- a/linear-maps.cabal
+++ b/linear-maps.cabal
@@ -1,5 +1,5 @@
 Name:           linear-maps
-Version:        0.6
+Version:        0.6.1
 Synopsis:       Finite maps for linear use
 Description:    
     Finite maps for linear use. 
@@ -99,7 +99,7 @@
         Data.IdMap.Core.Fast
 
     Build-Depends:
-        base == 4.1.*,
+        base >= 3.0,
         containers == 0.2.*,
         HUnit == 1.2.* 
 --        random