dispatcher: add link to algorithm definition to main section

src/modules/dispatcher/doc/dispatcher_admin.xml

@@ -1435,7 +1435,9 @@ modparam("dispatcher", "ds_interval_mode", 7200)
 				congestion detection" below.
 				</para>
 				<para>
-				The congestion estimation is done using an EWMA (see ds_latency_estimator_alpha).
+				The congestion estimation is done using an Exponentially Weighted Moving Average (EWMA).
+				More information about the algorithm can be found for example
+				<ulink url="http://www.itl.nist.gov/div898/handbook/pmc/section3/pmc324.htm">here</ulink>.
 				If all the gateways in a set are above their congestion threshold(weight), the
 				load distribution is instead done using the ratio of estimated congestion ms.
 				</para>