diff --git a/book/source/06-signatures.md b/book/source/06-signatures.md
index bb32d4a..466fe09 100644
--- a/book/source/06-signatures.md
+++ b/book/source/06-signatures.md
@@ -96,6 +96,12 @@ RFC Sections [5.2.3.11](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypt
 
 ### "Negotiating" signature hash algorithm based on recipients preference subpackets
 
+```{admonition} TODO
+:class: warning
+
+investigate, discuss: GnuPG uses preference packets for the User ID that was addressed while sequoia completely omits User ID preferences and either uses Direct Key Sigs or (I think) primary User ID.
+```
+
 ### Explore viability of having multiple signatures, e.g. v4+v6?
 
 ```{admonition} TODO
diff --git a/book/source/07-signing_data.md b/book/source/07-signing_data.md
index 03acb41..ef01e1d 100644
--- a/book/source/07-signing_data.md
+++ b/book/source/07-signing_data.md
@@ -15,6 +15,15 @@ Add content, including:
 
 - Signature of a canonical text document
   - "The signature is calculated over the text data with its line endings converted to `<CR><LF>`"
+  
+data signatures have three forms:
+- detached,
+- inline (that is signature contains the data which is signed inside of a signature container) and
+- cleartext which I guess will be special-cased in v6 (to require small text etc).
+ 
+(This corresponds to gnupg's --detach-sign --sign and --clear-sign)
+
+cleartext: explain text transforms for cleartext signatures (LF->CRLF etc)
 ```
 
 ## Data signatures