diff --git a/book/source/03-cryptography.md b/book/source/03-cryptography.md
index 6dcd73e..839fd19 100644
--- a/book/source/03-cryptography.md
+++ b/book/source/03-cryptography.md
@@ -133,8 +133,10 @@ Digital signatures in OpenPGP are used in two primary contexts:
 - [Signatures on components](component_signatures_chapter)
 
 (hybrid_cryptosystems)=
-## Hybrid cryptosystems in OpenPGP
+## Hybrid cryptosystems
 
 [Hybrid cryptosystems](https://en.wikipedia.org/wiki/Hybrid_cryptosystem) combine the use of symmetric and asymmetric (public-key) cryptography to capitalize on the strengths of each, namely symmetric cryptography's speed and efficiency and public-key cryptography's mechanism for secure key exchange.
 
+### Usage and terminology in OpenPGP
+
 OpenPGP uses a hybrid cryptosystem for encryption.  This approach involves generating unique shared secrets, known as "session keys," for each session. For detailed information on this topic, please refer to the chapters {ref}`encryption_chapter` and {ref}`decryption_chapter`.