diff --git a/book/source/04-certificates.md b/book/source/04-certificates.md
index 29b2fef..52f6026 100644
--- a/book/source/04-certificates.md
+++ b/book/source/04-certificates.md
@@ -102,7 +102,7 @@ Subkeys have the same structure as the primary key, but they are used in a diffe
 OpenPGP certificates can contain a number of subkeys
 ```
 
-#### Key Flags: defining which operations a component key can perform
+#### Key flags: defining which operations a component key can perform
 
 Each component key has a set of ["Key Flags"](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#key-flags) that specify which operations that key can perform.
 
@@ -245,7 +245,7 @@ Note: certification signatures [can be made irrevocable](https://www.ietf.org/ar
 This section only contains notes and still needs to be written
 ```
 
-### Certificate Management / Evolution of a certificate over time
+### Certificate management / Evolution of a certificate over time
 
 Minimized versions, merging, effective "append only" semantics, ...
 
@@ -262,7 +262,7 @@ Minimized versions, merging, effective "append only" semantics, ...
 - Subkey: Revoked/key expired/binding signature expired
 - User ID: revoked, binding expired, ...
 
-### Best Practices regarding Key Freshness
+### Best practices regarding Key Freshness
 
 ```{admonition} TODO
 :class: warning
@@ -273,7 +273,7 @@ Minimized versions, merging, effective "append only" semantics, ...
 Wiktor suggests to check: https://blogs.gentoo.org/mgorny/2018/08/13/openpgp-key-expiration-is-not-a-security-measure/ for important material
 ```
 
-### Metadata Leak of Social Graph
+### Metadata leak of Social Graph
 
 (unbound_user_ids)=
 ### Adding unbound User IDs to a certificate