Cite Thomas Ptacek for urandom
diff --git a/docs/random-numbers.rst b/docs/random-numbers.rst
index cd73a7b..12969d1 100644
--- a/docs/random-numbers.rst
+++ b/docs/random-numbers.rst
@@ -8,8 +8,8 @@
provide a cryptographically secure random number generator, which can result in
major security issues depending on the algorithms in use.
-Therefore, it is our recommendation to always use your operating system's
-provided random number generator, which is available as ``os.urandom()``. For
+Therefore, it is our recommendation to `always use your operating system's
+provided random number generator`_, which is available as ``os.urandom()``. For
example, if you need 16 bytes of random data for an initialization vector, you
can obtain them with:
@@ -18,3 +18,5 @@
>>> import os
>>> os.urandom(16)
'...'
+
+.. _`always use your operating system's provided random number generator`: http://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers/