diff --git a/guidelines.html b/guidelines.html
index 7826570..156fd5a 100644
--- a/guidelines.html
+++ b/guidelines.html
@@ -293,9 +293,10 @@ <h5>Extra-archetypal contamination</h5>
                       </td>
                     </tr>
                   </table>
-                  <p>In both cases, it is encoded by added the necesseray missing node 
-                    (i.e., the original and the witness outside the tree from which the contamination, with no label,
-                    and indicating the necessary contaminations.</p> 
+                  <p>In both cases, it is encoded by added the necesseray missing node to turn the representation into the standard directed graph,
+                    with a single root. That means: 1. adding an unnamed root, 2. adding the missing hypothetical node, outside of the archetypal tradition,
+                    that is the source of the contamination, 3. signaling the contamination from this outside missing node to the contaminated witness.
+                    </p> 
                   <table style="width:100%">
                     <tr>
                       <td>Extra-archetypal <br/>contamination</td>