diff --git a/README.md b/README.md
index cb817d7..69dfc1b 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,11 @@
 # Core Ontology of Phenotypes (COP)
 
+## Introduction
+
 COP is a core ontology, which can be used to specify phenotype algorithms as ontologies (Phenotype Algorithm Specification Ontology, PASO).
 
-![COP overview](images/cop.png)
\ No newline at end of file
+![COP overview](images/cop.png)
+
+## References
+
+Uciteli, A; Beger, C; Kirsten, T; Meineke, FA; Herre, H: *Ontological Modelling and Reasoning of Phenotypes.* Proceedings of the Joint Ontology Workshops 2019; Graz; Austria; September 23-25; 2019. [PDF](http://ceur-ws.org/Vol-2518/paper-ODLS11.pdf)
\ No newline at end of file