diff --git a/SUMMARY.md b/SUMMARY.md
index 1c3f326..56e5103 100644
--- a/SUMMARY.md
+++ b/SUMMARY.md
@@ -23,9 +23,8 @@
   * [Caching](protocol/caching.md)
 * [Message](message/README.md)
   * [Message Formats](message/message-formats.md)
+  * [Error Reporting](message/error-reporting.md)  
   * [Content Negotiation](message/content-negotiation.md)
-  * [Siren](message/siren.md)
-  * [Error Reporting](message/error-reporting.md)
   * [JSON](message/json.md)
 * [Evolution](evolution/README.md)
   * [Changes and Versioning](evolution/versioning.md)
diff --git a/message/content-negotiation.md b/message/content-negotiation.md
index e69de29..d02ebfa 100644
--- a/message/content-negotiation.md
+++ b/message/content-negotiation.md
@@ -0,0 +1,27 @@
+# Content Negotiation
+Every API MUST implement and every API Consumer MUST use [HTTP content negotiation](https://tools.ietf.org/html/rfc7231#section-3.4) where a representation of a resource is requested.
+
+> NOTE: The content negotiation plays the key role in evolving an API, **change management and versioning**.
+
+#### Example
+A client is programmed to understand the `application/vnd.example.resource+json; version=2` message format semantics. The client requests a representation of the `/greeting` resource in desired the media type (including its version) from the server:
+
+```
+GET /greeting HTTP/1.1
+Accept: application/vnd.example.resource+json; version=2
+...
+```
+
+The server is able to provide only a newer version of the requested media type `version=2.1.3`. But since the newer version is backward compatible with the requested `version=2` (related: Changes & Versioning) it is able to satisfy the request and responds:
+
+```
+HTTP/1.1 200 OK
+Content-Type: application/vnd.example.resource+json; version=2.1.3
+...
+```
+
+> NOTE: A server that doesn't have the requested representation media type available MUST respond with the HTTP Status Code **406 Not Acceptable**. 
+> 
+> NOTE: A server MAY have multiple choices available and MAY respond with the **300 Multiple Choices** response. In which case client SHOULD choose from the presented choices.
+> 
+> You can read more about content negotiation at [MDN Content negotiation](https://developer.mozilla.org/en-US/docs/Web/HTTP/Content_negotiation).
diff --git a/protocol/content-negotiation.md b/protocol/content-negotiation.md
deleted file mode 100644
index d02ebfa..0000000
--- a/protocol/content-negotiation.md
+++ /dev/null
@@ -1,27 +0,0 @@
-# Content Negotiation
-Every API MUST implement and every API Consumer MUST use [HTTP content negotiation](https://tools.ietf.org/html/rfc7231#section-3.4) where a representation of a resource is requested.
-
-> NOTE: The content negotiation plays the key role in evolving an API, **change management and versioning**.
-
-#### Example
-A client is programmed to understand the `application/vnd.example.resource+json; version=2` message format semantics. The client requests a representation of the `/greeting` resource in desired the media type (including its version) from the server:
-
-```
-GET /greeting HTTP/1.1
-Accept: application/vnd.example.resource+json; version=2
-...
-```
-
-The server is able to provide only a newer version of the requested media type `version=2.1.3`. But since the newer version is backward compatible with the requested `version=2` (related: Changes & Versioning) it is able to satisfy the request and responds:
-
-```
-HTTP/1.1 200 OK
-Content-Type: application/vnd.example.resource+json; version=2.1.3
-...
-```
-
-> NOTE: A server that doesn't have the requested representation media type available MUST respond with the HTTP Status Code **406 Not Acceptable**. 
-> 
-> NOTE: A server MAY have multiple choices available and MAY respond with the **300 Multiple Choices** response. In which case client SHOULD choose from the presented choices.
-> 
-> You can read more about content negotiation at [MDN Content negotiation](https://developer.mozilla.org/en-US/docs/Web/HTTP/Content_negotiation).