more references

docs/04-multiple-components.md

@@ -73,7 +73,7 @@ When you create a React component instance, you can include additional React com
 <Parent><Child /></Parent>
 ```
 
-`Parent` can read its children by accessing the special `this.props.children` prop.
+`Parent` can read its children by accessing the special `this.props.children` prop. **`this.props.children` is an opaque data structure:** use the [React.Children utilities](/react/docs/top-level-api.html#react.children) to manipulate them.
 
 
 ### Child Reconciliation

tips/07-children-props-type.md

@@ -49,3 +49,5 @@ var GenericWrapper = React.createClass({
 
 React.renderComponent(<GenericWrapper>hello</GenericWrapper>, mountNode);
 ```
+
+To make `this.props.children` easy to deal with, we've provided the [React.Children utilities](/react/docs/top-level-api.html#react.children).