diff --git a/StageSonification2012.bib b/StageSonification2012.bib
index 9f42b5e..3fd3b36 100644
--- a/StageSonification2012.bib
+++ b/StageSonification2012.bib
@@ -325,7 +325,8 @@
 	year = {1992}
 },
 
-@misc{drenckhan_presentation_????,
+@misc{drenckhan_presentation_2012,
 	title = {A presentation on liquid foams},
-	author = {Drenckhan, Wiebke}
+	author = {Drenckhan, Wiebke},
+	year = {2012}
 }
\ No newline at end of file