diff --git a/urls.txt b/urls.txt
index c482f65..f4baac6 100644
--- a/urls.txt
+++ b/urls.txt
@@ -23,7 +23,6 @@ https://www.cl.cam.ac.uk/~rja14/Papers/SEv3-ch21-mar17.pdf
 https://www.cl.cam.ac.uk/~rja14/Papers/SEv3-ch22-jul10.pdf
 https://www.cl.cam.ac.uk/~rja14/Papers/SEv3-ch23-jun5.pdf
 https://www.cl.cam.ac.uk/~rja14/Papers/SEv3-ch24-3aug.pdf
-https://www.cl.cam.ac.uk/~rja14/Papers/SEv3-ch25-jul10.pdf
 https://www.cl.cam.ac.uk/~rja14/Papers/SEv3-ch26-3aug.pdf
 https://www.cl.cam.ac.uk/~rja14/Papers/SEv3-ch27-3aug.pdf
 https://www.cl.cam.ac.uk/~rja14/Papers/SEv3-ch28-3aug.pdf