mention another dkim private publication guide

policy/tpa-rfc-15-email-services.md

@@ -407,7 +407,7 @@ Other things to be careful about:
  * watch out for [DKIM replay attacks][]
 
  * decide key rotation policy (how frequently, should we [publish
-   private keys][])
+   private keys][], see also [this guide][])
 
 [ARC]: http://arc-spec.org/
 [OpenARC]: https://github.com/trusteddomainproject/OpenARC
@@ -415,6 +415,7 @@ Other things to be careful about:
 [email policy problem]: https://gitlab.torproject.org/tpo/tpa/team/-/issues/40404
 [publish private keys]: https://blog.cryptographyengineering.com/2020/11/16/ok-google-please-publish-your-dkim-secret-keys/
 [DKIM replay attacks]: https://utcc.utoronto.ca/~cks/space/blog/spam/DKIMSpamReplayAttack
+[this guide]: https://rya.nc/dkim-privates.html
 
 ### Security concerns