diff --git a/README.md b/README.md
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@@ -5,9 +5,15 @@ Directories
 
 * `/ulo`: Playing around w/ the results of the ULO paper [1, 2]
 
+* `/graphdb`: Playing with the RDF4J [3] API of GraphDB [4].
+
 References
 ==========
 
 [1] https://kwarc.info/people/mkohlhase/papers/cicm19-ulo.pdf
 
 [2] https://gl.mathhub.info/ulo/ulo/blob/master/ulo.owl
+
+[3]  https://rdf4j.org/
+
+[4] http://graphdb.ontotext.com/