temporalintro.html: TGRASS reference paper added

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@58556 15284696-431f-4ddb-bdfa-cd5b030d7da7

temporal/temporalintro.html

@@ -141,8 +141,17 @@ input space time raster dataset or a subset of it.
 
 <h4>Statistics and gap filling</h4>
 
- 
 <ul>
     <li><a href="t.rast.gapfill.html">t.rast.gapfill</a></li>
     <li><a href="t.rast.univar.html">t.rast.univar</a></li>
 </ul>
+
+<h4>See also</h4>
+
+<ul>
+<li>Gebbert, S., Pebesma, E., 2014. TGRASS: A temporal GIS for field based
+    environmental modeling. Environmental Modelling &amp; Software 53, 1-12.
+    (<a href="http://dx.doi.org/10.1016/j.envsoft.2013.11.001">DOI</a>)</li>
+</ul>
+
+