diff --git a/SDT/schema4.0/docs/SDT_Components.md b/SDT/schema4.0/docs/SDT_Components.md
index 2a629f4b5161b0ba4c177e6f53bc1ef31fe7e4eb..ef4adb5c3a6030d9ac165d445bce2ae3ff9432de 100644
--- a/SDT/schema4.0/docs/SDT_Components.md
+++ b/SDT/schema4.0/docs/SDT_Components.md
@@ -69,6 +69,7 @@ It can also be used to collect all specified [ModuleClasses](#ModuleClasses), [D
 - **Imports** : XML import/include of other XML files / SDT templates. Optional.  
 Note, that when using **Imports** one must include the following namespace in the Domain-Element definition, as shown in the example below: ```xmlns:xi="http://www.w3.org/2001/XInclude"```
 - **[DataTypes](#DataType)** : A list of *DataTypes* that are global to the whole domain. They can be referenced from other definitions by the [Extend](#Extend) element. Optional.
+- **[SubDevices](#SubDevice)** : a List of *SubDevice* components. They can be referenced from other SubDevice definitions by the [Extend](#Extend) element. Optional.
 - **[ModuleClasses](#ModuleClass)** : A list of those *ModuleClass* components that are global to the whole domain. Optional.
 - **[DeviceClasses](#DeviceClass)** : a List of *DeviceClass* components. Optional.
 - **[ProductClasses](#ProductClass)** : a List of *ProductClass* components. Optional.
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