better presentation of lambda-delta

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       </p>
 
       <h2>The Formal System &lambda;&delta; (lambda-delta)<a name="lambda-delta"></a></h2>
+      
+      <p>The formal system &lambda;&delta; is a typed &lambda;-calculus that
+         pursues the unification of terms, types, environments and contexts
+        as the main goal.
+         &lambda;&delta; takes some features from the Automath-related
+        &lambda;-calculi and some from the pure type systems, but differs
+        from both in that it does not include the &Pi; construction while it
+        provides for an abbreviation mechanism at the level of terms.
+      </p>
+
+      <p> The development presents the proofs of some important properties that
+          &lambda;&delta; enjoys. In particular: 
+          <ul> <li> the confluence of reduction </li>
+               <li> the correctness of types </li>
+               <li> the uniqueness of types up to conversion </li>
+               <li> the subject reduction of the type assignment </li>
+               <li> the strong normalization of the typed terms </li>
+               <li> the decidability of type inference problem </li>
+          </ul>
+      </p>
+      
       <p>
-      See the <a href="http://helm.cs.unibo.it/lambda-delta/">&lambda;&delta; home page</a>.
+       See the <a href="http://helm.cs.unibo.it/lambda-delta/">&lambda;&delta; home page</a>
+       for more information.
       </p>
 
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