create an AnimationResources.java file in which...

AnimationsResources.java

package com.projectname.project.client.resources;

import com.arcbees.gsss.animation.client.AnimationResources;
import com.google.gwt.resources.client.ClientBundle;

public interface AnimationsResources extends ClientBundle {

    interface Style extends AnimationResources.Animation {
    }

    @Source({"com/arcbees/gsss/animation/client/animationsettings.gss",
            "com/arcbees/gsss/animation/client/animations.gss",
            "css/myStyle.gss"})
    Style style();
}