diff --git a/book/source/04-certificates.md b/book/source/04-certificates.md
index a6219b5..9550e3e 100644
--- a/book/source/04-certificates.md
+++ b/book/source/04-certificates.md
@@ -170,7 +170,7 @@ The primary User ID was historically the main store for preferences that apply t
 While 
 [user attributes](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-user-attribute-packet-tag-1) are similar to User IDs, they are less commonly used.
 
-Currently, the OpenPGP standard prescribes only one format to be stored in user attributes: an [image](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-the-image-attribute-subpack), in JPEG format. Typically, this image represents the key owner, although it is not required.
+Currently, the OpenPGP standard prescribes only one format to be stored in user attributes: an [image](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-the-image-attribute-subpack) in JPEG format. Typically, this image represents the key owner, although it is not required.
 
 ## Linking the components