Update template-functions-resource.md

Author: bmoore-msft

articles/azure-resource-manager/templates/template-functions-resource.md

@@ -477,7 +477,7 @@ Use `'Full'` when you need resource values that aren't part of the properties sc
 
 ### Valid uses
 
-The `reference` function can only be used in the properties of a resource definition and the outputs section of a template or deployment. When used with [property iteration](copy-properties.md), you can use the `reference` function for `input` because the expression is assigned to the resource property.
+The `reference` function can only be used in the outputs section of a template or deployment and properties object of a resource definition. It cannot be used for resource properties such as `type`, `name`, `location` and other top level properties of the resource definition. When used with [property iteration](copy-properties.md), you can use the `reference` function for `input` because the expression is assigned to the resource property.
 
 You can't use the `reference` function to set the value of the `count` property in a copy loop. You can use to set other properties in the loop. Reference is blocked for the count property because that property must be determined before the `reference` function is resolved.