Update the doxygen configuration file.
Minor updates/fixes to the source documentation.
diff --git a/doxygen/math.doxy b/doxygen/math.doxy
index 25b6090..72ec2e3 100644
--- a/doxygen/math.doxy
+++ b/doxygen/math.doxy
@@ -41,7 +41,7 @@
 # Configuration::addtions related to external references   
 #---------------------------------------------------------------------------
 TAGFILES               = tnl_dd.tag=../tnl_dd \
-                         core.tag=../core \
+                         main.tag=../core \
                          swrast.tag=../swrast \
                          swrast_setup.tag=../swrast_setup \
                          tnl.tag=../tnl \