diff --git a/bibliography.bib b/bibliography.bib
index 7f6d858..e76b1f0 100644
--- a/bibliography.bib
+++ b/bibliography.bib
@@ -126,7 +126,7 @@
   isbn      = {978-0-465-09760-9}
 }
 
-@article{koessler-2006,
+@book{koessler-2006,
 	author	= {Wolfgang Kössler},
 	title	= {Folien Stochastik},
 	year	= {2006},