diff --git a/book/source/08-signing_components.md b/book/source/08-signing_components.md
index 6958475..ff6e123 100644
--- a/book/source/08-signing_components.md
+++ b/book/source/08-signing_components.md
@@ -298,7 +298,9 @@ add diagrams?
 (wot)=
 ### Decentralized automated trust decisions; or, the "Web of Trust"
 
-The OpenPGP, the "Web of Trust" is a trust model that performs authentication decisions on a set of certifications and delegations.
+The OpenPGP, the "Web of Trust" is a trust model that performs authentication decisions on a set of certifications and delegations[^strong-set].
+
+[^strong-set]: In the context of the Web of Trust, the so-called [strong set](https://en.wikipedia.org/wiki/Web_of_trust#Strong_set) refers to a set of certificates that are strongly linked amongst each other via third-party certifications.
 
 The OpenPGP "Web of Trust" model assumes that every user makes their own choice about who they delegate authentication decisions to. Based on the available certificates and third-party signatures, the user's OpenPGP software uses the Web of Trust mechanism to determine which certificates are considered reliable for an identity.