diff --git a/docs/development/test-vectors.rst b/docs/development/test-vectors.rst
index be98c6f..2cd9faa 100644
--- a/docs/development/test-vectors.rst
+++ b/docs/development/test-vectors.rst
@@ -81,7 +81,8 @@
 * ``ecdsa_root.pem`` - `DigiCert Global Root G3`_, a ``secp384r1`` ECDSA root
   certificate.
 * ``verisign-md2-root.pem`` - A legacy Verisign public root signed using the
-  MD2 algorithm.
+  MD2 algorithm. This is a PEM conversion of the `root data`_ in the NSS source
+  tree.
 
 Custom X.509 Vectors
 ~~~~~~~~~~~~~~~~~~~~
@@ -221,3 +222,4 @@
 .. _`NIST PKI Testing`: http://csrc.nist.gov/groups/ST/crypto_apps_infra/pki/pkitesting.html
 .. _`testx509.pem`: https://github.com/openssl/openssl/blob/master/test/testx509.pem
 .. _`DigiCert Global Root G3`: http://cacerts.digicert.com/DigiCertGlobalRootG3.crt
+.. _`root data`: https://hg.mozilla.org/projects/nss/file/25b2922cc564/security/nss/lib/ckfw/builtins/certdata.txt#l2053