X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=docs%2Fusers_guide%2Fglasgow_exts.xml;h=fd6e32286d894c3b685ee68215ceedeb8c4cd2ec;hp=96c2ce9988ca899bd9739b9df0c3d98710a64f4b;hb=5e418599f051ecb88d9d2dbeea96563cf438b065;hpb=3c21579aa6365c053baf82680882a01949b1e902

diff --git a/docs/users_guide/glasgow_exts.xml b/docs/users_guide/glasgow_exts.xml
index 96c2ce9..fd6e322 100644
--- a/docs/users_guide/glasgow_exts.xml
+++ b/docs/users_guide/glasgow_exts.xml
@@ -2061,6 +2061,11 @@ something more specific does not:
     op = ... -- Default
 </programlisting>
 </para>
+<para>You can find lots of background material about the reason for these
+restrictions in the paper <ulink
+url="http://research.microsoft.com/%7Esimonpj/papers/fd%2Dchr/">
+Understanding functional dependencies via Constraint Handling Rules</ulink>.
+</para>
 </sect3>
 
 <sect3 id="undecidable-instances">