diff --git a/en_US/upgrade/0-upgrade.iredmail.1.4.2-1.4.3.md b/en_US/upgrade/0-upgrade.iredmail.1.4.2-1.4.3.md
index 3c44c748..bc5dbfdc 100644
--- a/en_US/upgrade/0-upgrade.iredmail.1.4.2-1.4.3.md
+++ b/en_US/upgrade/0-upgrade.iredmail.1.4.2-1.4.3.md
@@ -44,7 +44,9 @@ so that you can know which version of iRedMail you're running. For example:
     - FreeBSD
     - OpenBSD
 - Greatly improve the performance of http keep-alive connections over SSL by
-  enabling `ssl_session_cache` parameter.
+  enabling `ssl_session_cache` parameter. See also:
+    - [Speeding up TLS: enabling session reuse](https://vincent.bernat.ch/en/blog/2011-ssl-session-reuse-rfc5077)
+    - [ssl_session_cache in Nginx and the ab benchmark](https://www.peterbe.com/plog/ssl_session_cache-ab)
 - Add new ssl cipher: `EECDH+CHACHA20`. It requires openssl 1.1.0, which is
   available on:
     - CentOS 7 and later
diff --git a/html/upgrade.iredmail.1.4.2-1.4.3.html b/html/upgrade.iredmail.1.4.2-1.4.3.html
index 5a9e21d3..a0468513 100644
--- a/html/upgrade.iredmail.1.4.2-1.4.3.html
+++ b/html/upgrade.iredmail.1.4.2-1.4.3.html
@@ -69,7 +69,11 @@ contributions. See also:
 </ul>
 </li>
 <li>Greatly improve the performance of http keep-alive connections over SSL by
-  enabling <code>ssl_session_cache</code> parameter.</li>
+  enabling <code>ssl_session_cache</code> parameter. See also:<ul>
+<li><a href="https://vincent.bernat.ch/en/blog/2011-ssl-session-reuse-rfc5077">Speeding up TLS: enabling session reuse</a></li>
+<li><a href="https://www.peterbe.com/plog/ssl_session_cache-ab">ssl_session_cache in Nginx and the ab benchmark</a></li>
+</ul>
+</li>
 <li>Add new ssl cipher: <code>EECDH+CHACHA20</code>. It requires openssl 1.1.0, which is
   available on:<ul>
 <li>CentOS 7 and later</li>