Reformat AES CTR vectors to use NIST loader & document their source properly
diff --git a/docs/development/test-vectors.rst b/docs/development/test-vectors.rst
index 3b8632e..97b5c34 100644
--- a/docs/development/test-vectors.rst
+++ b/docs/development/test-vectors.rst
@@ -47,7 +47,8 @@
 Symmetric Ciphers
 ~~~~~~~~~~~~~~~~~
 
-* AES (CBC, CFB, CTR, ECB, GCM, OFB) from `NIST CAVP`_.
+* AES (CBC, CFB, ECB, GCM, OFB) from `NIST CAVP`_.
+* AES CTR from :rfc:`3686`.
 * 3DES (CBC, CFB, ECB, OFB) from `NIST CAVP`_.
 * ARC4 from :rfc:`6229`.
 * Blowfish (CBC, CFB, ECB, OFB) from `Bruce Schneier's vectors`_.