diff --git a/bibliography.bib b/bibliography.bib
index 47df644..7f6d858 100644
--- a/bibliography.bib
+++ b/bibliography.bib
@@ -125,3 +125,11 @@
   address   = {New York},
   isbn      = {978-0-465-09760-9}
 }
+
+@article{koessler-2006,
+	author	= {Wolfgang Kössler},
+	title	= {Folien Stochastik},
+	year	= {2006},
+	address	= {Humboldt-Universität zu Berlin},
+	url	= {https://www2.informatik.hu-berlin.de/~koessler/Stochastik/Stochastik2006/FolienStochastik_4.pdf}
+}