diff --git a/book/source/06-signatures.md b/book/source/06-signatures.md
index 7dc8b2f..e995c26 100644
--- a/book/source/06-signatures.md
+++ b/book/source/06-signatures.md
@@ -140,7 +140,7 @@ In the OpenPGP protocol, each {term}`signature subpacket<OpenPGP Signature Subpa
 
 This mechanism accounts for different {term}`OpenPGP implementations<OpenPGP Implementation>` that may support only certain subsets of the standard. Moreover, it anticipates the evolution of the standard, including the addition of new {term}`subpacket types<OpenPGP Signature Subpacket Type>`.
 
-Consider a scenario where an {term}`implementation<OpenPGP Implementation>` does not recognize a {term}`subpacket<OpenPGP Signature Subpacket>` indicating {term}`signature<OpenPGP Signature Packet>` {term}`expiration`. Without understanding this concept, the {term}`implementation<OpenPGP Implementation>` might erroneously accept an already {term}`expired<Expiration>` {term}`signature<OpenPGP Signature Packet>`. By marking the {term}`expiration date subpacket` as {term}`critical<Criticality Flag>`, the creator of the {term}`signature<OpenPGP Signature Packet>` ensures that any recipient who cannot process this {term}`subpacket<OpenPGP Signature Subpacket>` will reject the {term}`signature<OpenPGP Signature Packet>` as {term}`invalid<Validation>`.
+Consider a scenario where an {term}`implementation<OpenPGP Implementation>` does not recognize a {term}`subpacket<OpenPGP Signature Subpacket>` indicating {term}`signature<OpenPGP Signature Packet>` {term}`expiration`. Without understanding this concept, the {term}`implementation<OpenPGP Implementation>` might erroneously accept an already {term}`expired<Expiration>` {term}`signature<OpenPGP Signature Packet>`. By marking the {term}`signature expiration time subpacket` as {term}`critical<Criticality Flag>`, the creator of the {term}`signature<OpenPGP Signature Packet>` ensures that any recipient who cannot process this {term}`subpacket<OpenPGP Signature Subpacket>` will reject the {term}`signature<OpenPGP Signature Packet>` as {term}`invalid<Validation>`.
 
 For specific guidelines on which {term}`subpackets<OpenPGP Signature Subpacket>` should be marked as {term}`critical<Criticality Flag>`, refer to the {term}`RFC` sections [5.2.3.11](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-signature-creation-time) to [5.2.3.36](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-intended-recipient-fingerpr).
 
diff --git a/book/source/23-glossary.md b/book/source/23-glossary.md
index 4819c9a..ea3ba1e 100644
--- a/book/source/23-glossary.md
+++ b/book/source/23-glossary.md
@@ -96,9 +96,6 @@ Encryption Key Flag
 Expiration
     A mechanism by which a {term}`Component` is invalidated due to the {term}`Expiration Time` of its {term}`binding signature` being older than the {term}`Reference Time` by which it is validated.
 
-Expiration Date Subpacket
-    An {term}`OpenPGP Signature Subpacket Type` which defines the {term}`Expiration Time` for an {term}`OpenPGP Signature Packet`.
-
 Expiration Time
     The time of expiry of an {term}`OpenPGP Signature Packet`.
 
@@ -297,6 +294,11 @@ Session Key
 Signature
     See {term}`OpenPGP Signature Packet`.
 
+Signature Expiration Time Subpacket
+    An {term}`OpenPGP Signature Subpacket Type` which defines the {term}`Expiration Time` for an {term}`OpenPGP Signature Packet`.
+
+    See [RFC 5.2.3.18](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-signature-expiration-time)
+
 Signature On Component
     {term}`Cryptographic signature` associated with {term}`Component Keys<Component Key>` or {term}`Identity Components<Identity Component>`. See [](/08-signing_components).