def get_institute_graph_url(start, end):
    """ Pie chart comparing institutes usage. """

    filename = get_institute_graph_filename(start, end)
    urls = {
        'graph_url': urlparse.urljoin(GRAPH_URL, filename + ".png"),
        'data_url': urlparse.urljoin(GRAPH_URL, filename + ".csv"),
    }

    return urls