Using ClientBundle in Vaadin

Hi All,
I would like to use a 3rd party component in my Vaadin application, and I need to use ClientBundle for this. 
I read this https://vaadin.com/forum#!/thread/1959965 but I get an error:
"The annotation @ClientBundle.Source is disallowed for this location"

My source root is: com.zamek.project, and I made a client.resources folder in it. There is an svg image in it and an iterface which inherits ClientBundle:

public interface PlazaResources extends ClientBundle {

        @Source("e1.svg")
        ExternalSVGResource page1;

}

Do I need to set somewhere  it is a client side? 

thx,
Zamek

Oh I found it, I forget to make page1 to method! 

  @Source("e1.svg")
        ExternalSVGResource page1();