private static List<Shape> buscarRefCat(List<Shape> shapes, String ref){

		List<Shape> shapeList = null;

		for(Shape shape : shapes) 
			if (shape != null && shape.getRefCat() != null && shape.getRefCat().equals(ref)){
				if (shapeList == null)
					shapeList = new ArrayList<Shape>();
				shapeList.add(shape);
			}

		return shapeList;
	}